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  • 251.
    Landström, Anders
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Elliptical Adaptive Structuring Elements for Mathematical Morphology2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    As technological advances drives the evolution of sensors as well as the systems using them, processing and analysis of multi-dimensional signals such as images becomes more and more common in a wide range of applications ranging from consumer products to automated systems in process industry. Image processing is often needed to enhance or suppress features in the acquired data, enabling better analysis of the signals and thereby better use of the system in question. Since imaging applications can be very different, image processing covers a wide range of methods and sub-fields.Mathematical morphology constitutes a well defined framework for non-linear image processing based on set relations. It relies on minimum and maximum values over neighborhoods (i.e. regions surrounding the individual points) defined by shapes or functions known as structuring elements. Classical morphological operations use a predefined structuring element which is used repeatedly for each point in the image. This is often not ideal, however, which has motivated the evolution of adaptive morphological filtering where the structuring element changes from point to point. The field of adaptive mathematical morphology includes many different concepts with different strengths and weaknesses, and the specific choice of method should be made with the specific application in mind.The main contribution of this thesis is a novel method for adaptive morphological filtering using Elliptical Adaptive Structuring Elements (EASE). The method enhances directional structures in images by orienting the structuring elements along the existing structure, and can be efficiently used to close gaps in such structures. The method is introduced by summarizing underlying theory as well as presenting a practical application motivating it:~crack detection in casted steel. Furthermore, it is demonstrated how the method can be extended to allow for filtering of incomplete (i.e. partially missing) image data without need for pre-filtering. The EASE concept is also put in relation to other related work by presenting a survey of the field of adaptive mathematical morphology.In conclusion, EASE allows for fast structure-based adaptive morphological filtering of images based on solid mathematical theory, successfully enhancing directional structures such as lines, borders, etc. in the data. The method is user-friendly, as it does not require more than a few user-defined parameters, and can also be adapted for direct filtering of incomplete data.

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  • 252.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonsson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Simonsson, Arne
    Wireless Access Networks, Ericsson Research, Luleå, Sweden.
    Voronoi-based ISD and site density characteristics for mobile networks2012Ingår i: 2012 IEEE 76th Vehicular Technology Conference: VTC2012-Fall: Towards Sustainable Mobility; Proceedings, Piscataway, NJ: IEEE Communications Society, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Inter-Site Distance (ISD) is a common measure for characterizing the site density in a mobile network However, obtaining a good estimation of the ISD for a real world network is not trivial since the physical layout is usually quite more complex than a perfect theoretical hexagonal grid, due to a number of unavoidable factors such as site availability and traffic density. Voronoi diagrams have been suggested for approximating cells from network layouts, providing a method for partitioning the covered area into cells defined by the proximity to the given set of sites. This yields a framework for site coverage approximation based on the actual site distribution, rather than an underlying theoretical model.We present a novel measure, based on Voronoi diagrams, for characterizing the site density of a cellular network and provide a comparison to the more traditional ISD measure. This measure improves capacity assessments and modeling of real networks.

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  • 253.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nellros, Frida
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Jonsson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Thurley, Matthew
    Image reconstruction by prioritized incremental normalized convolution2011Ingår i: Image analysis: 17th Scandinavian conference, SCIA 2011, Ystad, Sweden, May 2011 ; proceedings / [ed] Anders Heyden; Fredrik Kahl, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2011, s. 176-185Konferensbidrag (Refereegranskat)
    Abstract [en]

    A priority-based method for pixel reconstruction and incrementalhole filling in incomplete images and 3D surface data is presented.The method is primarily intended for reconstruction of occluded areasin 3D surfaces and makes use of a novel prioritizing scheme, based on apixelwise defined confidence measure, that determines the order in whichpixels are iteratively reconstructed. The actual reconstruction of individualpixels is performed by interpolation using normalized convolution.The presented approach has been applied to the problem of reconstructing3D surface data of a rock pile as well as randomly sampled imagedata. It is concluded that the method is not optimal in the latter case,but the results show an improvement to ordinary normalized convolutionwhen applied to the rock data and are in this case comparable to thoseobtained from normalized convolution using adaptive neighborhood sizes.

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  • 254.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Thurley, Matthew J.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Adaptive morphology using tensor-based elliptical structuring elements2013Ingår i: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 34, nr 12, s. 1416-1422Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mathematical Morphology is a common strategy for non-linear filtering of image data. In its traditional form the filters used, known as structuring elements, have constant shape once set. Such rigid structuring elements are excellent for detecting patterns of a specific shape, but risk destroying valuable information in the data as they do not adapt in any way to its structure.We present a novel method for adaptive morphological filtering where the local structure tensor, a well-known method for estimation of structure within image data, is used to construct adaptive elliptical structuring elements which vary from pixel to pixel depending on the local image structure. More specifically, their shape varies from lines in regions of strong single-directional characteristics to disks at locations where the data has no prevalent direction.

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  • 255.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Thurley, Matthew J.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Morphology-based crack detection for steel slabs2012Ingår i: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 6, nr 7, s. 866-875Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Continuous casting is a highly efficient process used to produce most of the world steel production tonnage, but can cause cracks in the semi-finished steel product output. These cracks may cause problems further down the production chain, and detecting them early in the process would avoid unnecessary and costly processing of the defective goods. In order for a crack detection system to be accepted in industry, however, false detection of cracks in non-defective goods must be avoided. This is further complicated by the presence of scales; a brittle, often cracked, top layer originating from the casting process. We present an approach for an automated on-line crack detection system, based on 3D profile data of steel slab surfaces, utilizing morphological image processing and statistical classification by logistic regression.The initial segmentation successfully extracts 80\% of the crack length present in the data, while discarding most potential pseudo-defects (non-defect surface features similar to defects). The subsequent statistical classification individually has a crack detection accuracy of over 80\% (with respect to total segmented crack length), while discarding all remaining manually identified pseudo-defects. Taking more ambiguous regions into account gives a worst-case false classification of 131~mm within the 30~600~mm long sequence of 150~mm wide regions used as validation data. The combined system successfully identifies over 70\% of the manually identified (unambiguous) crack length, while missing only a few crack regions containing short crack segments.The results provide proof-of-concept for a fully automated crack detection system based on the presented method.

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  • 256.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonsson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Adaptive Morphological Filtering of Incomplete Data2014Ingår i: 2013 International Conference on Digital Image Computing: Techniques and Applications (DICTA 2013): Hobart, Australia, 26-28 Nov. 2013, Piscataway, NJ: IEEE Communications Society, 2014, artikel-id 6691479Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate how known convolution techniques for uncertain data can be used to set the shapes of structuring elements in adaptive mathematical morphology, enabling robust morphological processing of partially occluded or otherwise incomplete data. Results are presented for filtering of both gray-scale images containing missing data and 3D profile data where information is missing due to occlusion effects. The latter demonstrates the intended use of the method: enhancement of crack signatures in a surface inspection system for casted steel.The presented method is able to disregard unreliable data in a systematic and robust way, enabling adaptive morphological processing of the available information while avoiding any false edges or other unwanted features introduced by the values of faulty pixels.

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  • 257.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Jonsson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Sub-millimeter crack detection in casted steel using color photometric stereo2014Ingår i: 2013 International Conference on Digital Image Computing Techniques and Applications (DICTA 2013: Hobart, Australia, 26-28 November 2013, Piscataway, NJ: IEEE Communications Society, 2014, artikel-id 6691532Konferensbidrag (Refereegranskat)
    Abstract [en]

    A novel method for automated inspection of small corner cracks in casted steel is presented, using a photometric stereo setup consisting of two light sources of different colors in conjunction with a line-scan camera. The resulting image is separated into two different reflection patterns which are used to cancel shadow effects and estimate the surface gradient. Statistical methods are used to first segment the image and then provide an estimated crack probability for each segmented region. Results show that true cracks are successfully assigned a high crack probability, while only a minor proportion of other regions cause similar probability values. About 80% of the cracks present in the segmented regions are given a crack probability higher than 70%, while the corresponding number for other non-crack regions is only 5%. The segmented regions contain over 70% of the manually identified crack pixels. We thereby provide proof-of-concept for the presented method.

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  • 258.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Transmitter Localization for 5G mmWave REMs by Stochastic Generalized Triangulation2016Ingår i: 23rd International Conference on Telecommunications (ICT 2016), Piscataway, NJ: IEEE Communications Society, 2016, s. 789-793, artikel-id 7500413Konferensbidrag (Refereegranskat)
    Abstract [en]

    Future mobile networks will need new tools to deal with the challenges of emerging technologies. In particular, more flexible networks will require localization of transmitters in the networks. In this work we present a novel method for transmitter localization, suitable for rich multipath mmWave 5G scenarios such as dense urban environments. Our work combines stochastic estimation of Radio Environmental Maps (REMs) with the well known concept of triangulation, generalizing the latter into a method for localization in anisotropic propagation environments. It can be considered a conceptual bridge from classical distance-based triangulation into a generalized version where the propagation environment is taken into account. The result is a highly flexible tool for network planning in general and transmitter localization in particular.

  • 259.
    Landström, Anders
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Simonsson, Arne
    Ericsson Research AB, Sweden.
    Thurfjell, Magnus
    Ericsson Research AB, Sweden.
    Ökvist, Peter
    Ericsson Research AB, Sweden.
    Measurement-Based Stochastical mmWave Channel Modeling2016Ingår i: 2016 IEEE Globecom Workshops (GC Wkshps), Piscataway, NJ: IEEE Communications Society, 2016, artikel-id 7848959Konferensbidrag (Refereegranskat)
    Abstract [en]

    Emerging mmWave technology will require newchannel models. Compared to the lower frequency bands,mmWaves will be more reflected and absorbed but less diffracted.Hence, placement of individual physical structures in the en-vironment will affect the propagation much more than before,providing a challenge for channel modeling. At the same time,however, an increasing amount of information about the topologyof the physical environment, in particular for buildings, is madeavailable through better measurement equipment and servicesfor obtaining 3D data. We propose a Monte-Carlo approachfor channel modeling where interactions between mmWaves andthe surrounding small-scale environment can be included, givena stochastic representation. This method is not only suitablefor assessment of basic effects such as material reflection andabsorption, but can also in the future be extended to variousadditional effects such as weather, traffic, foliage, etc. Theframework is verified against 15 GHz measurements from anurban environment, demonstrating how major reflection pathscan be replicated by modeling the closest buildings.IndexTerms

  • 260.
    Landström, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Luleå tekniska universitet, Institutionen för system- och rymdteknik, CDT.
    Arenas, Julia Martinez
    Ecole National Supérieure de Télecommunications, Site de Toulouse, Toulouse, France.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Luleå tekniska universitet, Institutionen för system- och rymdteknik, CDT.
    Börjesson, Per Ola
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Luleå tekniska universitet, Institutionen för system- och rymdteknik, CDT.
    Boucheret, Marie-Laure
    Ecole National Supérieure de Télecommunications, Site de Toulouse, Toulouse, France.
    Ödling, Per
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Luleå tekniska universitet, Institutionen för system- och rymdteknik, CDT.
    Time and frequency offset estimation in OFDM systems employing pulse shaping1997Ingår i: Bridging the way to the 21st century: 1997 IEEE 6th International Conference on Universal Personal Communications record ; 12 - 16 October 1997, Hotel Del Coronado, San Diego, CA, USA ; conference record, Piscataway, NJ: IEEE Communications Society, 1997, s. 279-283Konferensbidrag (Refereegranskat)
    Abstract [en]

    Time and frequency offset estimation is addressed in an OFDM system that uses a cyclic prefix and pulse shaping. Earlier work has presented a method that avoids the use of pilots by exploiting the inherent correlation in the cyclically extended OFDM symbol. In this paper this technique is extended to include systems with pulse shaping. The joint Maximum Likelihood estimator of time and frequency offsets for such systems is presented and evaluated. An implementable structure of the extended estimator is given. Simulations show that it is possible to maintain the performance when introducing pulse shaping into an OFDM system.

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  • 261.
    Landström, Daniel
    et al.
    Lund University, Dept. of Applied Electronics, SE-221 00 Lund, Sweden.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    van de Beek, Jaap
    Nokia Svenska AB, Box 1070, SE-164 25 Kista, Sweden.
    Ödling, Per
    Lund University, Dept. of Applied Electronics, SE-221 00 Lund, Sweden.
    Börjesson, Per Ola
    Lund University, Dept. of Applied Electronics, SE-221 00 Lund, Sweden.
    Symbol time offset estimation in coherent OFDM systems1999Ingår i: IEEE International Conference on Communications: ICC '99, Piscataway, NJ: IEEE Communications Society, 1999, Vol. 1, s. 500-505Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a symbol time offset estimator for coherent OFDM systems. This estimator exploits both the redundancy in the cyclic prefix and the pilot symbols used for channel estimation. The estimator is robust against frequency offsets and is suitable for use in dispersive channels. We base the estimator on the ML estimator for the AWGN channel. Simulations of an example system indicate a system performance as close as 0.3 dB to a perfectly synchronized system. Compared to an estimator not using pilots, our estimator's performance could allow a shorter cyclic prefix and thus a more spectrally efficient system.

  • 262.
    Landström, Daniel
    et al.
    Luleå tekniska universitet. Lund Institute of Technology, Lund University, Sweden.
    Ödling, Per
    Department of Applied Electronics, Lund University.
    Börjesson, Per Ola
    Luleå tekniska universitet. Lunds universitet, Lund Institute of Technology, Department of Applied Electronics.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Uplink OFDM synchronization of future multiuser radio systems1999Ingår i: Proceedings of radiovetenskap och kommunikation: Karlskrona 14-17 juni 1999 / RVK 99 / [ed] Jan-Olof Gustafsson, Karlskrona: Högskolan i Karlskrona/Ronneby , 1999Konferensbidrag (Refereegranskat)
  • 263. Leblanc, James
    Multichannel autoregressive modeling and spectral estimation methods for airborne radar environment: final report for Summer faculty research program - Rome Develoment Laboratory1996Rapport (Övrigt vetenskapligt)
  • 264. Leblanc, James
    On fractionally-spaced equalizer design for digital microwave radio channels1995Ingår i: Conference Record of the Twenty-Ninth Asilomar Conference on Signals, Systems and Computers, IEEE Communications Society, 1995, s. 290-294Konferensbidrag (Refereegranskat)
    Abstract [en]

    Advances in blind identification of fractionally-spaced models for digital communication channels and blind fractionally-spaced equalizer adaptation rely on the assumption that the time span chosen for the fractionally-spaced equalizer exceeds that of the channel. This paper considers time-domain design formulas minimizing the mean-squared symbol recovery error achieved by a finite-length FIR fractionally-spaced equalizer with a time span shorter than the channel impulse response time span for white zero-mean QAM sources in the presence of white zero-mean channel noise. For minimum mean-squared error designs the symbol error rates achievable are plotted versus the ratio of the source variance to the channel noise variance (with the channel model power normalized to achieve a received signal of unit variance) for different fractionally-spaced equalizer lengths on 64-QAM for several T/2-spaced channel models derived from experimental data. Our intent is to fuel the ongoing debate about fractionally-spaced equalizer length selection .

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  • 265. Leblanc, James
    et al.
    Castro, Julio
    New Mexico State University.
    Model order selection for multidimensional innovations based detection in airborne radar1998Ingår i: Challenges in radar systems and solutions: proceedings of the 1998 IEEE Radar Conference, Dallas, Texas, May 11 - 14, 1998 / [ed] Scott Ramey, Piscataway, NJ: IEEE Communications Society, 1998, s. 141-146Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the model order selection problem for use with the multidimensional autoregressive (MAR) process in airborne radar detection processing which uses an innovations based detection algorithm (IBDA). Results indicate that a low order model should be used to accurately portray the return signal spectrum. Specifically, this paper investigates the use of the Akaike (1971) information criterion for model order selection. Examples are included for physically modeled data sets as well as actual radar data sets

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  • 266. Leblanc, James
    et al.
    Chaine, M.D.
    Proximity effects of `unused' output buffers on ESD performance [CMOS]1991Ingår i: Reliability physics 1991: 29th annual proceedings, [1991 International Reliability Physics Symposium], Las Vegas, Nevada, April 9, 10, 11, 1991, New York: IEEE Communications Society, 1991, s. 327-330Konferensbidrag (Refereegranskat)
    Abstract [en]

    A unique failure mechanism, identified on an unused output buffer located near a used input protection device, occurs when excessive substrate current is generated during an electrostatic discharge (ESD) event. This new mechanism, the proximity effect, plays an important role when the n moat region of an input ESD circuit is within 20 μm of an unrelated n moat diffusion region contacted to the power supply, V cc. The operation of the most commonly used ESD input protection circuitry when stressed with respect to Vcc is reviewed. A laser cut experiment has verified that disconnecting the Vcc bus from the unused n moats eliminates this type of ESD failure. Device metal mask changes have confirmed these findings. This ESD failure mechanism, has been demonstrated on a variety of I/O buffer layouts, and a solution has been identified

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  • 267. Leblanc, James
    et al.
    Chung, Wonzoo
    Cornell University, Ithaca.
    The local minima of fractionally-spaced CMA blind equalizer costfunction in the presence of channel noise1998Ingår i: Proceedings of the 1998 IEEE International Conference on Acoustics, Speech, and Signal Processing: May, 12 - 15, 1998, Washington State Convention and Trade Center, Seattle, Washington, USA, Piscataway, NJ: IEEE Communications Society, 1998, s. 3345-3348Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the local minima relocation of the fractionally spaced constant modulus algorithm (FSE-CMA) cost function in the presence of noise. Local minima move in a particular direction as the noise power increases and their number may be eventually reduced. In such cases the performance of FSE-CMA may fail to adequately reduce intersymbol interference (ISI), but achieve an approximated MMSE by reducing its equalizer noise gain under certain constraints. We analyze the mechanism of relocation of the FSE-CMA cost function local minima in terms of the auto-correlation matrix of the sub-channel convolution matrix and its eigenvectors

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  • 268. Leblanc, James
    et al.
    De Leon, Philiph L.
    New Mexico State University.
    Speech separation by kurtosis maximization1998Ingår i: Proceedings of the 1998 IEEE International Conference on Acoustics, Speech, and Signal Processing: May, 12 - 15, 1998, Washington State Convention and Trade Center, Seattle, Washington, USA, Piscataway, NJ: IEEE Communications Society, 1998, s. 1029-1032Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a computationally efficient method of separating mixed speech signals. The method uses a recursive adaptive gradient descent technique with the cost function designed to maximize the kurtosis of the output (separated) signals. The choice of kurtosis maximization as an objective function (which acts as a measure of separation) is supported by experiments with a number of speech signals as well as spherically invariant random processes (SIRPs) which are regarded as excellent statistical models for speech. Development and analysis of the adaptive algorithm is presented. Simulation examples using actual voice signals are presented

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  • 269.
    Leblanc, James
    et al.
    Klipsch School of ECE, New Mexico State University, Las Cruces, NM, USA.
    De Léon, Philip L.
    Klipsch School of ECE, New Mexico State University, Las Cruces, NM, USA.
    Source separation of speech signals using kurtosis maximization1997Ingår i: Proceedings of the 35th Allerton Conference on Communication, Control and Computing, University of Illinois Press, 1997Konferensbidrag (Refereegranskat)
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  • 270.
    Leblanc, James
    et al.
    School of Electrical Engineering, Cornell University, Ithaca, NY, United States.
    Dogancay, K.
    Dept. of Systems Engineering, RSISE, Australian National University, Canberra, 0200, ACT, Australia.
    Kennedy, Rodney A.
    Dept. of Systems Engineering, RSISE, Australian National University, Canberra, 0200, ACT, Australia.
    Johnson, Jr., C. Richard
    School of Electrical Engineering, Cornell University, Ithaca, NY, United States.
    Effects of input data correlation on the convergence of blind adaptive equalizers1994Ingår i: ICASSP-94: 1994 IEEE International Conference on Acoustics, Speech and Signal Processing, April 19 - 22, 1994, Adelaide Convention Centre, Adelaide, South Australia; [proceedings], Piscataway, NJ: IEEE Communications Society, 1994, s. III/313-III/316Konferensbidrag (Refereegranskat)
    Abstract [en]

    A variety of blind equalization algorithms exist. These algorithms, which draw on some theoretical justification for the demonstration or analysis of their purportedly ideal convergence properties, almost invariably rely on the input data being independent and identically distributed (i.i.d.). In contrast, in this paper we show that input correlation can have a marked effect on the character of algorithm convergence. We demonstrate that under suitable input data correlation and channels: (i) undesirable local minima present in the i.i.d. case are absent for certain correlated sources implying ideal global convergence for some situations and, (ii) the most commonly employed practical algorithm can exhibit ill-convergence to closed-eye minima even under the popular single spike initialization when an eye-opening equalizer parameterization is possible.

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  • 271.
    Leblanc, James
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fijalkow, Inbar
    University of Cergy-Pontoise.
    Blind adapted, pre-whitened constant modulus algorithm2001Ingår i: Where minds meet: 2001 IEEE International Conference on Communications ; ICC 2001. June 11 - 14, 2001 ; Helsinki ; conference re / [ed] Yrjö Neuvo, Piscataway, NJ: IEEE Communications Society, 2001, Vol. 8, s. 2438-2442Konferensbidrag (Refereegranskat)
    Abstract [en]

    We examine the use of a blind adaptive “pre-whitening” filter to precede an equalizer adapted by the constant modulus algorithm (CMA). The idea is based on results presented in which the use of a (fixed, or non-adaptive) pre-whitening filter provides an isometry (i.e. geometry preserving transformation) between the combined channel-equalizer (or global space) and the equalizer tap space. As much analysis found in CMA literature is done in “global space” now applies to the pre-whitened “equalizer tap space”, considerable exploitation of a known geometric structure is now possible. This paper’s main result demonstrates a method for improving the convergence rates of CMA adapted equalizers using the results of prewhitening analysis. The slow convergence of CMA equalizers is a common negative point associated with this well-known, robust blind equalization algorithm.

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  • 272.
    Leblanc, James
    et al.
    Department of Elec. Engineering, Rochester Institute of Technology, Rochester, NY, USA.
    Fijalkow, Inbar
    ENSEA/ETIS, 6 avenue du Ponceau, 95014 Cergy-Pontoise Cdx, France.
    Johnson, Jr., C. Richard
    School of Elec. Engineering, Cornell University, Ithaca, NY, USA.
    Fractionally-spaced constant modulus algorithm blind equalizer error surface characterization: effects of source distributions1996Ingår i: Conference Proceedings: ICASSP 96, Piscataway, NJ: IEEE Communications Society, 1996, s. 2944-2947Konferensbidrag (Refereegranskat)
    Abstract [en]

    The constant modulus algorithm (CMA) is a popular blind equalization algorithm. A common device used in demonstrating the convergence properties of CMA is the assumption that the source sequence is i.i.d. (independent, identically distributed). Previous results in the literature show that a finite length fractionally-spaced equalizer allows for perfect equalization of moving average channels (under certain channel conditions known as zero-forcing criteria). CMA has previously been shown to converge to such perfectly equalizing settings under an independent, platykurtic source. This paper investigates the effect of the distribution from which an independent source sequence is drawn on the CMA error surface and stationary points in the perfectly-equalizable fractionally-sampled equalizer case. Results include symbolic identification of all stationary points, as well as the eigenvalues and eigenvectors associated with their Hessian matrix. Results show quantitatively the loss of error surface curvature (in both direction and magnitude) at all stationary points. Simulations included demonstrate the affect this has on convergence speed.

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  • 273. Leblanc, James
    et al.
    Gatine, G.
    Marquet, D.
    Management unit for reliable power supply stations for use in telecommunication facilities1989Ingår i: Eleventh International Telecommunications Energy Conference. INTELEC '89. Conference Proceedings, Poscataway, NJ: IEEE Communications Society, 1989, s. 9.3/1-9.3/4Konferensbidrag (Refereegranskat)
    Abstract [en]

    Following a general presentation of the system architectures for two types of reliable energy stations, GEODE and ALFATEL, used in telecommunication facilities, the authors describe the concept of a centralized management system covering several energy stations situated at different geographical locations. The role of communication with the power supply station monitoring units is then described. This makes it possible to define the functions carried out by the management unit, some of which may be operated through remote control by staff on standby duty. The functions of remote monitoring of processes, statistical studies, inventories, background records, man/machine relationships, and maintenance assistance are backed up by a PC-type machine .

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  • 274. Leblanc, James
    et al.
    Johnson, Jr., C. Richard
    Toward operational guidelines for memoryless-error-function-style blind equalizers1992Ingår i: Proceedings 2nd COST 229 Workshop on Adaptive Algorithms in Communications, 1992, s. 5-17Konferensbidrag (Refereegranskat)
  • 275. Leblanc, James
    et al.
    Jr, C. Richard Johnson
    Cornell University, Ithaca.
    Global CMA error surface characteristics, source statistic effects: polytopes and manifolds1997Ingår i: 1997 13th International Conference on Digital Signal Processing proceedings, Piscataway, NJ: IEEE Communications Society, 1997Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work focuses on gaining insight to CMA behavior through identi cation of global properties of CMA stationary point locations due to source statistics (distributions and temporal correlation). The CMA error function under source correlation effects is viewed as a deformation of the iid CMA error surface. As deformations are the realm of topology, we look at some of the topological aspects connected with CMA source correlation. Some general characteristics of CMA under iid source are presented, noting relations to Morse Theory, polytopes, and Euler Characteristics.

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  • 276. Leblanc, James
    et al.
    Kennedy, Rodney A.
    Ryan, William E.
    Pre-cursor extended RAM-DFE canceler (PERC) nonlinear equalizer for nonlinear ISI channels1998Ingår i: Proceedings 1998 DSP Workshop, IEEE Signal Processing Society, 1998Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a nonlinear equalizer structure that provides effective and computationally efficient intersymbol interference (ISI) reduction for channels with nonlinearities. The technique makes use of a RAM-DFE structure enhanced with the ability to cancel pre-cursor nonlinear ISI. In many nonlinear channels, the distortion caused by the nonlinear element (such as a nonlinear power amplifier) and bandlimiting filters creates nonlinear ISI. Such distortion typically limits the system to loworder constellations (such as QPSK). Higher order constellation are possible only if effective reduction of the nonlinear ISI is achieved. The applicability of our nonlinear equalizer and its performance for a nonlinear satellite channel is included.

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  • 277. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Enhanced RAM-based equalizers for nonlinear channels1999Ingår i: 32nd Asilomar Conference on Signal, Systems and Computers, IEEE Communications Society, 1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a detection method for nonlinear channels with memory. This method uses a linear feedforward equalizer in conjunction with a random access memory (RAM) based (nonlinear) equalizer. The design criterion for the feedforward equalizer is non-traditional, with the intent to improve performance of the RAM-based equalizer. Development of the design criterion and a training-mode based adaptive implementation along with examples of this equalizer with a Pre-Cursor Enhanced RAM-DFE Canceller are included.

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  • 278. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Georgia Institute of Technology.
    Minimum mean square error channel truncation for magnetic channels1999Ingår i: Digest of INTERMAG 99, Piscataway, NJ: IEEE Communications Society, 1999, s. FS07-Konferensbidrag (Refereegranskat)
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  • 279. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Non-equiprobable constellation shaping and blind constant modulus algorithm equalization1996Ingår i: Proceedings of the 1996 Conference on Information Science and Systems : [CISS '96 held March 20,21, and 22, 1996 at Princeton University, Princeton, NJ], Princeton, NJ: Princeton University Press, 1996Konferensbidrag (Refereegranskat)
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  • 280. Leblanc, James
    et al.
    Meyer, W.E.
    Blind adaptive fractionally-spaced CMA in the presence of channel noise1996Ingår i: Proceedings of the 1996 Conference on Information Science and Systems: CISS'96, 1996, s. 373-374Konferensbidrag (Refereegranskat)
  • 281.
    Leblanc, James P.
    et al.
    School of Electrical Engineering, Cornell University, Ithaca, NY, USA.
    Fijalkow, Inbar
    ENSEA, Groupe ETIS, 95014 Cergy-Pontoise Cedex, France.
    Huber, Birkett
    Math Department, Cornell University, Ithaca, NY, USA.
    Johnson, Jr., C. Richard
    School of Electrical Engineering, Cornell University, Ithaca, NY, USA.
    Fractionally spaced CMA equalizers under periodic and correlated inputs1995Ingår i: Conference proceedings ICASSP-95: ICASSP-95, Piscataway, NJ: IEEE Communications Society, 1995, s. 1041-1044Konferensbidrag (Refereegranskat)
    Abstract [en]

    CMA fractionally spaced equalizers (CMA-FSEs) have been shown, under certain conditions, to be globally asymptotically convergent to a setting which provides perfect equalization. Such a result relies heavily on the assumptions of a white source and no channel noise (as is the case in much of the literature's analysis of CMA). Herein, we relax the white source assumption and examine the effect of source correlation on CMA. Analytic results are meshed with examples showing CMA-FSE source correlation effects. Techniques for finding all stationary and saddle points on the CMA-FSE error surface are presented using recent developments in the algebraic-geometry community.

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  • 282.
    Leblanc, James P.
    et al.
    Klipsch School of ECE, New Mexico State University, Las Cruces, NM, USA.
    Fijalkow, Inbar
    ENSEA/ETIS, 6 av. du Ponceau, 95014 Cergy-Pontoise Cdx, France.
    Johnson Jr., C. Richard
    Electrical Engineering Department, Cornell Univ. Ithaca, NY, USA.
    CMA fractionally spaced equalizers: Stationary points and stability under i.i.d. and temporally correlated sources1998Ingår i: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 12, nr 2, s. 135-155Artikel i tidskrift (Refereegranskat)
  • 283. Leblanc, James
    et al.
    Raghuveer, M.
    New Mexico State University.
    Wavelet transform based detection of photon-limited and low contrast objects1997Ingår i: ICASSP 97: International Conference on Acoustics, Speech, and Signal Processing, Munich, Germany, April 21 - 24, 1997, Piscataway, NJ: IEEE Communications Society, 1997, s. 3657-3660Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents methods for detection and localization of photon-limited objects in noise. As opposed to the correlation based or Fourier transform based techniques which exhibit sensitivity to object scaling, we propose a method based on the continuous wavelet transform with its ability to reject noise and to localize objects in space and time as well as in scale. An advantageous twist presented here is the use of the wavelet transform on the complex envelope of the signal of interest. This has the advantage of reducing "rippling" effects seen in the transform of the original waveform. An example of further post-processing on the wavelet-transformed data is provided

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  • 284.
    Lei, Xiangyu
    et al.
    Chalmers university of technology, Gothenburg, Sweden.
    Wirdelius, Håkan
    University West, Trollhättan, Sweden.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    The effect of ultrasound wave path estimation to defect characterization capability in half-skip total focusing method2023Ingår i: Research and Review Journal of Nondestructive Testing (ReJNDT), ISSN 2941-4989, Vol. 1, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The total focusing method (TFM) is a post-processing imaging technique applied on full matrix capture (FMC) ultrasonic inspection (UT) dataset. In TFM the ultrasonic wave energy is synthetically focused on every pixel in the image region of interest (ROI). In terms of half-skip TFM (HSTFM), wave mode conversion happens when the wave rebounds at interface, such as specimen backwall. This paper aims to propose and evaluate a method that involves Snell’s law to address accurate estimation of distanceof-flight (DOF) of wave propagation when wave mode conversion appears in HSTFM. This HSTFM algorithm is applied to both experimental and simulated FMC dataset that inspects a surface-breaking notch for notch image reconstruction. Comparisons between images with and without considering Snell’s law in wave mode conversion show visible difference that could lead to misinterpretations in characterizing the defect. The sensitivity of TFM to varying defect features such as defect tilt angle is also studied using simulated FMC datasets.

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  • 285.
    Lemlikchi, Safia
    et al.
    Center for Development of Advanced Technologies, Algiers, Algeria.
    Martinsson, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Djelouah, Hakim
    Université des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Parametric estimation of overlapping echoes reflected from coated media2021Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 178, artikel-id 107990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a parametric modeling strategy was used to investigate ultrasonic signals reflecting from coated structures. The model parameter vector is defined by the combined model consisting of hard and soft modeling. The hard model describes the overlap with pure delays, reflection and transmission coefficients. The soft model copes with a more realistic case when all ultrasonic losses are included. The estimation procedure follows the maximum likelihood approach and uses the Levenberg–Marquardt algorithm for optimizing the objective function. The tested waveforms were reflected from thermally sprayed Diamalloy 4060 coatings deposited on 310SS substrate with increasing degree of overlapping echoes. Measurements were carried out in pulse-echo mode using a 15 MHz nominal frequency transducer. A good prediction of overlapping signals was achieved. Reverberating coating echoes were successfully separated and coating properties (time-of-flight (TOF), ultrasonic velocity and attenuation) were directly deduced. Results show the potential of the method to investigate overlapping ultrasonic signals reflecting from highly attenuating layers such as thermal sprayed coatings. It also shows the ability for the method to make a complete separation of the overlapping echoes, not only between the substrate and the coating echoes, but also between the reverberations in the coating itself that has been neglected for a long time. This allows an accurate characterization of the coating properties.

  • 286.
    Lemlikchi, Safia
    et al.
    Division milieu ionisés et lasers, Centre de Developpement des Technologies Avancees, Algiers, Algeria.
    Martinsson, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hamrit, Ahmet
    ALGESCO, Blida, Algeria.
    Djelouah, Hakim
    Universite´ des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université d’Alger 1, Algiers, Algeria.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ultrasonic Characterization of Thermally Sprayed Coatings2019Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 3, s. 391-404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the simultaneous determination of the ultrasonic parameters in thermally sprayed coatings. The parameters of interest are the longitudinal wave velocity and the ultrasonic attenuation. The test materials are two cobalt-based coatings (FSX 414 and Diamalloy 4060), both deposited onto stainless steel (310SS) substrates. The ultrasonic measurements were carried out in the pulse-echo configuration using several transducers. The ultrasonic signals reflected from the coatings were successfully estimated using the combined model, together with the maximum likelihood estimation and the Levenberg–Marquardt approach. The best estimate was obtained for 20 MHz measurements. Once the model was validated, the ultrasonic parameters of the thermally sprayed coatings were extracted. Model validation is based on the analysis of the residual between measured and estimated signals. Results showed non-dispersive ultrasonic velocities with average values of (3940±50)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(3940±50)m/s(3940±50)m/s in Diamalloy 4060 and (4260±20)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(4260±20)m/s(4260±20)m/s in FSX 414. High ultrasonic attenuation with a quadratic frequency dependence was observed for both materials. Moreover, it was found that the ultrasonic parameters in thermally sprayed materials are microstructure dependent. For close densities, the harder the coating, the higher the ultrasonic wave velocity and attenuation.

  • 287.
    Lin, Jing
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Spares demand system with consideration of integration management and optimization2011Ingår i: 2011 International Conference on Mechanical, Industrial, and Manufacturing Engineering: MIME 2011, Melbourne, Australia, 15 January-16 January 2011, 2011, s. 1-4Konferensbidrag (Refereegranskat)
    Abstract [en]

    Inventory management differs from other manufacturing inventory managements, mainly due to its specialists in function with maintenance. So far, enormous attention has been paid by standing on spares’ manufacturingfactories, sales companies, end users’ purchasing departments, or maintenance engineers, separately. However, not only “bullwhip effect” in forecasting spares demands, but also deteriorated relationships among the spares supply chains have shown that, spares optimization strategies with isolated consideration couldonly bring short-term or partial improvements. In this paper, the spares demand system with consideration of integration management is promoted, the new Solid-Net relationships among four main components are elaborated. Then, the root causes of ineffective in spares demand system are analyzed. Also, distinctoptimization policies are illustrated. What’s more, successful stories in practice are cited.

  • 288.
    Lin, Jing
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Zhu, Huiming
    College of Business Administration, Hunan University.
    Bayesian survival analysis in reliability for complex system with a cure fraction2011Ingår i: International Journal of Performability Engineering, ISSN 0973-1318, Vol. 7, nr 2, s. 109-120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In traditional methods for reliability analysis, one complex system is often considered as being composed by some subsystems in series. Usually, the failure of any subsystem would be supposed to lead to the failure of the entire system. However, some subsystems' lifetimes are long enough and even never fail during the life cycle of the entire system. Moreover, such subsystems' lifetimes will not be influenced equally under different circumstances. In practice, such interferences will affect the model's accuracy, but it is seldom considered in traditional analysis. To address these shortcomings, this paper presents a new approach to do reliability analysis for complex systems. Here a certain fraction of the subsystems is defined as a "cure fraction" under the consideration that such subsystems' lifetimes are long enough and even never fail during the life cycle of the entire system. By introducing environmental covariates and the joint power prior, the proposed model is developed within the Bayesian survival analysis framework, and thus the problem for censored (or truncated) data in reliability tests can be resolved. In addition, a Markov chain Monte Carlo computational scheme is implemented and a numeric example is discussed to demonstrate the proposed model

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  • 289.
    Lindberg, Johanna
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Digitala tjänster och system.
    Trojer, Elmar
    Ericsson Research.
    Jobér, Johan
    Netmore.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Tiger, Jonas
    IT Norrbotten.
    Value chains, operator sharing models, and regulatory aspects2020Rapport (Övrigt vetenskapligt)
  • 290.
    Lindberg, Petter
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Integration of a Software-Defined Baseband for Nano Satellites2022Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The number of Nano satellites launched into space is increasing rapidly each year. All satellites need a ground station with a baseband to communicate with. Current commercial basebands for TT&C (telemetry, tracking and command) are using proven designs and are too expensive to be used for Nano satellites. This thesis investigates the feasibility to use a SDB (Software-Defined Baseband) for TT&C with Nano satellites in low earth orbit. It describes the making of a transceiver which is validated with simulated data,recorded data and live satellite passes. It also describes the implementation of a GPS (Global PositioningSystem), TCR (Time Code Receiver) and TCP/IP (Transmission Control Protocol/Internet Protocol)interface as well as the process of testing for EMC (Electromagnetic Compatability) requirements. A half-duplex transmit/receive system is also proposed. The SDB functioned acceptable for telemetry with Nano satellites with up to 90% of the data packets being received depending on which satellite that wasbeing tracked. The SDB needs further development, validation and certification to compete with today’scommercial basebands.

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  • 291.
    Linder, Kristoffer
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Optical Characterization of Lignin Nanoparticles2020Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Lignin är en av huvudbeståndsdelarna av trä och plantor som fungerar likt ett lim som ger mekanisk styrka. Lignin är en biopolymer, som består av tre fenylgrupper: p-hydroxifenyl (H), guaiacyl (G) och syringyl (S). På senaste tid har det visat sig att det är möjligt att tillverka lignin nanopartiklar, det är små sfäriska partiklar som är helt gjorda av lignin, som skulle kunna ersätta de miljöfarliga silver nanopartiklarna som i nuläget används i många olika tillämpningar. Lignin nanopartiklar kan potentiellt också användas som funktionella ytbeläggningar, såväl som biologiskt nedbrytbara lim och flottörer. Fem prover, av nanopartiklar, undersöktes i denna studie. Det första provet innehöll lignin nanopartiklar, det andra silver nanopartiklarna, och de tre återstående proverna innehöll ligninbelagda silver nanopartiklar, extraherade från aceton, tetrahydrofuran (THF) och dimetylformamid (DMF). Alla prover karakteriserades med hjälp av spektroskopiska metoder: infraröd- och mörkfältavbildning, liksom UV-Vis-, fluorescens- och Ramanspektroskopi.

    I denna avhandling visades att ligninbelagda silver nanopartiklar uppvisar ytplasmonsresonans, vilket inducerar en värmeeffekt vid infraröd bestrålning. För att identifiera ligninets fenylgrupper användes UV-Vis-spektroskopi. Det visade sig att spektra från proverna uppvisade flera intensiva band. Målet med UV-Vis-spektroskopin var att undersöka absorptionsegenskaperna hos de ligninbelagda silvernanopartiklarna. Möjliga ytplasmonresonansvåglängder bestämdes och två av fenylgrupperna identifierades.

    I denna studie användes Ramansspektroskopi för att definiera karakteristiska band för proverna. Detta gjordes för att undersöka om lignin nanopartiklarna har samma egenskaper som bulk lignin. Ramanspektroskopi ger information om ligninets struktur. Vidare identigierades p-hydroxifenyl-, guaiacyl- och syringylstrukturerna med en excitationsvåglängd på 532nm. En jämförelse av spektra för de lignininnehållande proverna indikerade att provernas Raman-kännetecken var liknande medan nästan inga tecken på silver fanns, vilket kan visa att partiklarna var täckta med lignin. Huvudsakliga ligninband kunde identifieras.

    Fluorescensegenskaperna, hos nanopartiklarna, undersöktes genom de erhållna emissionspektra efter exponering av blå-, grön- och UV-ljus. De erhållna spektra dekonvoluterades till dess gaussiska komponenter. Det visade sig att fluorescensen, efter exponering av UV-ljus, ökade med exponeringstiden.

    Mörkfältmikroskopi användes för att generera bilder på partiklarna. De resulterade i bilder med olika färger (vitt, gult, blått och rött) som motsvarade olika partikelstorlekar och geometrier. På så sätt kunde färhållandena mellan de olika partikelstorlekarna uppskattas.

    De ligninbelagda silver-nanopartiklarna, extraherade från aceton-lösningen, uppvisade en stark ytplasmonresonanseffekt, vilket kan bero på absorptionen (från absorptionsspektrat) vid 463nm. De ligninbelagda silver-nanopartiklarna, extraherade från DMF-lösningen, uppvisade en medelstark ytplasmonresonanseffekt, vilket kan bero på absorptionen vid 362nm. De ligninbelagda silver-nanopartiklarna, extraherade från THF-lösningen, uppvisade en svag ytplasmonresonanseffekt, vilket kan bero på absorptionen vid 379-380nm. De rena lignin- och silver-nanopartiklarna uppvisade endast uppvärmning men ingen ytplasmonresonanseffekt.

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  • 292. Linderhed, Anna
    et al.
    Lundberg, Magnus
    Nyberg, Sten
    Sjökvist, Stefan
    Uppsäll, Magnus
    Optical measurements of real minefields2002Ingår i: Detection and Remediation Technologies for Mines and Minelike Targets VII, / [ed] J. Thomas Broach; Russell S. Harmon; Gerald J. Dobeck, 2002, s. 160-171Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents preliminary analysis of the data from measurements on a minefield in Croatia done in the international cooperation project Airborne Minefield Area Reduction (ARC). Temperature differences above and around suspected mines and minefield indicators, were recorded with a long wave IR camera in 8-9 micrometers , over a time of several days, capturing data under different weather conditions. The data are compared to simulations of land mines, minefield indicators and other objects using a themodynamic FEM model, developed at FOI. Different detection methods are presented and applied to the data.

  • 293. Ling, Jun
    et al.
    Tan, Xing
    Li, Jian
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Efficient channel equalization for MIMO underwater acoustic communications2010Ingår i: 2010 IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM), Piscataway, NJ: IEEE Communications Society, 2010, s. 73-76Konferensbidrag (Refereegranskat)
    Abstract [en]

    Linear minimum mean-squared error (LMMSE)-based channel equalization is widely used in multi-input multioutput (MIMO) underwater acoustic communications (UAC). The practical challenge of LMMSE based schemes is the necessity of matrix inversion which generally imposes heavy computational burden on the receiver. To obtain the LMMSE filters efficiently, we exploit the conjugate gradient method and the diagonalization properties of circulant matrices. The proposed scheme is based on fast Fourier transform operations and can be implemented in parallel, which makes it a promising candidate for real-time MIMO underwater acoustic communications. Both numerical and SPACE'08 experimental examples are presented to demonstrate the effectiveness of the proposed approach.

  • 294.
    Ling, Jun
    et al.
    University of Florida.
    Tan, Xing
    University of Florida.
    Yardibi, Tarik
    University of Florida.
    Li, Jian
    University of Florida.
    He, Hao
    University of Florida.
    Nordenvaad, Magnus Lundberg
    Enhanced channel estimation and efficient symbol detection in MIMO underwater acoustic communications2009Ingår i: Conference Record of the Forty-Third Asilomar Conference on Signals, Systems and Computers, IEEE Communications Society, 2009, s. 600-604Konferensbidrag (Refereegranskat)
    Abstract [en]

    Effective training sequences and reliable channel estimation algorithms are essential for enhancing the performance of multi-input multi-output (MIMO) underwater acoustic communications (UAC). Also, effective interference cancellation schemes are crucial for reliable symbol detection. In this paper, the problem of designing MIMO training sequences is considered. Moreover, we present a sparse learning via iterative minimization (SLIM) algorithm for enhanced channel estimation and reduced computational complexity. Furthermore, RELAX-BLAST, a linear minimum mean-squared error based symbol detection scheme, is implemented efficiently by exploiting the conjugate gradient method and diagonalization properties of circulant matrices. The proposed MIMO UAC techniques are evaluated using both simulated and experimental examples.

  • 295.
    Ling, Jun
    et al.
    Department of Electrical and Computer Engineering, University of Florida.
    Zhao, Kexin
    Department of Electrical and Computer Engineering, University of Florida.
    Li, Jian
    Department of Electrical and Computer Engineering, University of Florida.
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Multi-input multi-output underwater communications over sparse and frequency modulated acoustic channels2011Ingår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 130, nr 1, s. 249-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses multi-input multi-output (MIMO) communications over sparse acoustic channels suffering from frequency modulations. An extension of the recently introduced SLIM algorithm, which stands for sparse learning via iterative minimization, is presented to estimate the sparse and frequency modulated acoustic channels. The extended algorithm is referred to as generalization of SLIM (GoSLIM). The sparseness is exploited through a hierarchical Bayesian model, and because GoSLIM is user parameter free, it is easy to use in practical applications. Moreover this paper considers channel equalization and symbol detection for various MIMO transmission schemes, including both space-time block coding and spatial multiplexing, under the challenging channel conditions. The effectiveness of the proposed approaches is demonstrated using in-water experimental measurements recently acquired during WHOI09 and ACOMM10 experiments.

  • 296.
    Lundberg, Georg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Polyphase Symbol Timing Synchronization on a Software-Defined Radio2021Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Software-defined radio is a continuously developing technology applied in fields of mobile communications and among others. It is a radio communication system where software is used to implement parts of its functionality in an embedded system or computer. Devices which can transmit and receive different radio protocols based on software has major advantages. The ability to be able to reconfigure and change functionality on the fly to adapt to different environments is suited for multiple different applications, one of such is the environment in space. Distortions such as phase, frequency and timing offset all occur in such environment. The effects of these distortions can be reduced using different synchronization techniques in the receiver. A polyphase symbol timing synchronizer with two different timing error detectors, is designed in Simulink consisting of an 8-tap polyphase filter bank, a zero-crossing or Gardner timing error detector, a second order Phase-locked loop and a numerically controlled oscillator. The initial design uses floating-point precision. A fixed-point model is implemented using Xilinx System Generator and is used to generate a custom IP. Simulation is done by implementing a transceiver model with Simulink for the transmitter and parts of the receiver. The polyphase symbol timing synchronizer locks after about 4000 symbols for lower signal-to-noise and the Gardner timing error detector performs better than the zero-crossing error detector at higher signal-to-noise ratios. 

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  • 297. Lundberg, Magnus
    Electro-optical land mine detection: and contributions to iterative decoding and power estimation2001Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 298. Lundberg, Magnus
    Land mine detection using dual-band electro-optical sensing2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 299.
    Lundberg, Magnus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Power aware design of COTS-based embedded Internet systems2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    An embedded system is a small autonomous computer system that is encapsulated in the device it is controlling. Examples of device with embedded systems are TVs, microwaves, and dishwashers. A modern car can hold as much as 60 microprocessors. Embedded systems sales are rapidly increasing. In fact processor sales for embedded system are much larger than those for personal computers. PC processors only represents 2 percent of all processor sales. The division of EISLAB at Luleå University of Technology focuses on research on Embedded internet systems (EIS). Embedded Internet Systems are embedded systems used to collect, process and distribute data over the Internet. EIS devices is a rapidly growing field. The reduced physical size and price of EIS sensors make them attractive to use in a wide range of applications such as; environmental monitoring, industrial, health care, and military surveillance. The vision of EISLAB is sensors with lifetimes in the range of years that will fit within a few cubic centimeters. The sensors developed at EISLAB are based on commercial-of-the-shelf-components (COTS). Using COTS-components reduces development time and cost for prototypes and small series products. All communication is handled using standardized protocols to give the device access to available communication infrastructure, such as cellular networks and the Internet. As most of the nodes are battery operated the dominant constraint for EIS devices is power consumption. This thesis presents our work to address this topic at a high level of abstraction. The first paper includes the development of a power aware design methodology for EIS devices. In the second paper the proposed design methodology is applied to a bluetooth-equipped device. The third paper discusses the problem of reducing power consumption of an always connected EIS device, showing the tradeoffs between power consumption and response time.

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  • 300. Lundberg, Magnus
    et al.
    Brown, C. L.
    Modelling of occluded signatures with application to optical detection of surface laid land mines2003Ingår i: Proceedings of the International Conference on Requirements and Technologies for the Detection, Removal and Neutralization of Landmines and UXO (EUDEM2-SCOT): Brussels, Belgium, September 2003., 2003Konferensbidrag (Refereegranskat)
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