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  • 1.
    Acharya, Sarthak
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Chouhan, Shailesh Singh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Scalability of Copper-Interconnects down to 3μm on Printed Boards by Laser-assisted-subtractive process2019Inngår i: Proceedings of: 2019 IMAPS Nordic Conference on Microelectronics Packaging (NordPac), IEEE, 2019, s. 206-209Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As per the latest roadmap of iNEMI, the global electronics market is emphasizing to identify disruptive technologies that can contribute towards denser, robust and tighter integration on the board level. Therefore, reduction in packaging factor of printed board can accommodate greater number of ICs to support miniaturization. This paper has shown an experimental method to pattern the metallic layer on a Printed circuit Board (PCB) to the smallest feature size. To investigate this, a commercially available FR-4 PCB with photosensitive material coat and a Copper (Cu) layer on it, is used. A reverse-mode Laser assisted writing is implemented to pattern the desired copper tracks. Soon after, a well-controlled development and chemical etching of the Laser-activated regions are done using Sodium Hydroxide solution followed by an aqueous solution of Sodium Persulfate. Current PCB interconnects used by the industries are of the order (~20 μm). Whereas the present work is a contribution towards achieving Copper interconnects with feature size 3.0μm. This miniaturization corresponds to 70% reduction in the feature size from 20 μm to 3μm. The natural adhesion of the Cu layer has remained intact even after the etching, shows the efficiency of the method adopted. Also, variation in the parameters such as etching time, etchant solution concentrations, temaperature, gain and exposure time of Laser beam and their corresponding effects are discussed. Other highlights of this subtractive method includes its cost-efficiency, lesser production time and repeatability.

  • 2.
    Adewumi, Oluwatosin
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Liwicki, Foteini
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Liwicki, Marcus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Conversational Systems in Machine Learning from the Point of View of the Philosophy of Science—Using Alime Chat and Related Studies2019Inngår i: Philosophies, ISSN 2409-9287, Vol. 4, nr 3, artikkel-id 41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This essay discusses current research efforts in conversational systems from the philosophy of science point of view and evaluates some conversational systems research activities from the standpoint of naturalism philosophical theory. Conversational systems or chatbots have advanced over the decades and now have become mainstream applications. They are software that users can communicate with, using natural language. Particular attention is given to the Alime Chat conversational system, already in industrial use, and the related research. The competitive nature of systems in production is a result of different researchers and developers trying to produce new conversational systems that can outperform previous or state-of-the-art systems. Different factors affect the quality of the conversational systems produced, and how one system is assessed as being better than another is a function of objectivity and of the relevant experimental results. This essay examines the research practices from, among others, Longino’s view on objectivity and Popper’s stand on falsification. Furthermore, the need for qualitative and large datasets is emphasized. This is in addition to the importance of the peer-review process in scientific publishing, as a means of developing, validating, or rejecting theories, claims, or methodologies in the research community. In conclusion, open data and open scientific discussion fora should become more prominent over the mere publication-focused trend.

  • 3.
    Adjrad, M.
    et al.
    University of Leeds.
    Aguado, L.E.
    Advanced Digital Institute.
    Daly, M.
    University of Leeds.
    Kemp, A.
    University of Leeds.
    Junered, Marcus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Lindström, J.
    Luleå tekniska universitet.
    Akos, Dennis
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Mangin, F.
    France Developpement Conseil.
    Interference monitoring for GNSS bands in indoor and urban environments2007Inngår i: Proceedings of the 20th International Technical Meeting of the Satellite Division of the Institute of Navigation: ION GNSS 2007, Institute of Navigation, The , 2007, Vol. 4, s. 1211-1220Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A collaborative research project between the University of Leeds and Luleå University of Technology, Sweden, has taken place aiming to characterize the man-made noise in urban and indoor environments in the Galileo allocated frequency bands: E5 (1191.795 ± 25.575 MHz), E6 (1278.75 ± 20 MHz), and L1 (1575.42 ± 16 MHz), obviously, also covering the GPS L1 and L5 bands. This project has been co-funded by the European GNSS Supervisory Authority (EGSA), with funding from the 6th Framework Program of the European Community for research and technological development. The project includes the development of two receiver systems: the first instrument is based on the use of a spectrum analyzer (SA-based instrument), a wideband GNSS antenna, and a front-end capable of capturing each Galileo band separately using appropriate filtering and switches. The second instrument addresses the issues of cost and portability, providing interference detection and alarm triggering without the need for complex instrument. This is accomplished using low cost components in a small form factor where the instrument is based on a core GNSS front-end. This instrument will only cover the L1/E1 band. The interference measurement is obtained by combining the information from the automatic gain control (AGC) voltage that controls the AGC amplifier gain and the spectrum analysis of the analogue-to-digital converter (ADC) output raw data. The AGC information will be very important for detecting the presence of wideband interference signals where this will be difficult using spectrum analysis (in contrast to the case to narrowband interference signals). Control and data logging from both instruments are performed using a laptop computer where the spectrum analyzer traces and the FE-based instrument data are recorded for offline analysis via a suite of MATLAB® scripts. This paper describes the spectrum survey conducted at various indoor and urban locations, operationally significant to GNSS, in the North of the UK. The survey sites were selected to obtain geographically diverse measurement results and provide a general representation of the spectral environment. In addition, the temporal variation of man-made noise (MMN) is considered, this latter being correlated with the human activity at the measurement site, by performing the measurements day and night, weekdays and weekends.

  • 4.
    Ahlmark, Daniel Innala
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Haptic Navigation Aids for the Visually Impaired2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Assistive technologies have improved the situation in society for visually impaired individuals.The rapid development the last decades have made both work and education much more accessible. Despite this, moving about independently is still a major challenge, one that at worst can lead to isolation and a decreased quality of life. To aid in the above task, devices exist to help avoid obstacles (notably the white cane), and navigation aids such as accessible GPS devices. The white cane is the quintessential aid and is much appreciated, but solutions trying to convey distance and direction to obstacles further away have not made a big impact among the visually impaired. Onefundamental challenge is how to present such information non-visually. Sounds and synthetic speech are typically utilised, but feedback through the sense of touch (haptics) is also used, often in the form of vibrations. Haptic feedback is appealing because it does not block or distort sounds from the environment that are important for non-visual navigation. Additionally, touch is a natural channel for information about surrounding objects, something the white cane so successfully utilises. This doctoral thesis explores the question above by presenting the development and evaluations of dierent types of haptic navigation aids. The goal has been to attain a simple user experience that mimics that of the white cane. The idea is that a navigation aid able to do this should have a fair chance of being successful on the market. Theevaluations of the developed prototypes have primarily been qualitative, focusing on judging the feasibility of the developed solutions. They have been evaluated at a very early stage, with visually impaired study participants.Results from the evaluations indicate that haptic feedback can lead to solutions that are both easy to understand and use. Since the evaluations were done at an early stage in the development, the participants have also provided valuable feedback regarding design and functionality. They have also noted many scenarios throughout their daily lives where such navigation aids would be of use.The thesis document these results, together with ideas and thoughts that have emerged and been tested during the development process. This information contributes to the body of knowledge on dierent means of conveying information about surrounding objects non-visually.

  • 5.
    Ahlmark, Daniel Innala
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    The Development of a Virtual White Cane Using a Haptic Interface2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For millions of visually impaired individuals worldwide, independent navigation is a major challenge. The white cane can be used to avoid obstacles close-by, but it does not aid in navigation as it is difficult to get a large-scale view of the environment. Technological aids have been developed, notably ones based on GPS, but they have not been widely adopted. This thesis approaches the problem from different perspectives. Firstly, current navigation aids are examined from a user-interaction perspective, leading to some design guidelines on how to present spatial information non-visually. Secondly, a prototype of a new navigation aid (the Virtual White Cane) is proposed, and a field trial with visually impaired participants is described. The idea behind the Virtual White Cane is to utilise the intuitive way humans avoid obstacles by touch, and specifically to leverage the experience white cane users already have. This is accomplished by scanning the environment with a laser rangefinder, and presenting the range information using a haptic interface. The regular white cane is easy to use because it behaves like an extended arm, and so does the Virtual White Cane, albeit working at a much greater distance than the regular cane. A field trial with six experienced white cane users was conducted to assess the feasibility of this kind of interaction. The participants carried out a trial procedure where they traversed a prepared environment using the Virtual White Cane. They did not receive extensive training prior to the trial, the point being that if the Virtual White Cane behaves like a regular one, it should be quick to learn for a white cane user. The results show that spatial information can be feasibly conveyed using a haptic interface. This is demonstrated by the ease with which the field trial participants familiarised themselves with the system, notably adopting a similar usage pattern. In interviews that were conducted following the trial procedures, the participants expressed interest in the idea and thought that being a white cane user helped them use the Virtual White Cane. Despite knowing how to operate the system, the participants found locating objects to be difficult. An extended training period would likely have made this easier, but this problem could also be lessened by understanding what model parameters (such as the length of the virtual cane) should be used.

  • 6.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Fredriksson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Den seende rullstolen2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In its current form, the white cane has been used by visually impaired people for almost a hundred years. It is an intuitive device that helps visually impaired people navigate independently. For people who, in addition to a visual impairment, also have impaired movement, this independence is not as certain. If a wheelchair or a walker is needed, human assistance might be a necessity.MICA (Mobile Internet Connected Assistant) is a computerized wheelchair that has been equipped with a laser rangefinder that can measure the distance to obstacles in the environment. This information has been used to make the wheelhair able to drive on its own, avoiding obstacles, so that users unable to drive a wheelchair themselves are able to use it.The latest addition to MICA - a virtual white cane - allows visually impaired wheelchair users to virtually touch obstacles in their environment, and thus navigate in a similar way to those using a regular white cane. This is accomplished by generating a simplified 3D model based on the data acquired from the laser rangefinder, and sending this data to a haptic device, allowing users to feel the 3D model.The virtual white cane is still in an early development stage. The first test drive of MICA with the virtual white cane (together known as "The Sighted Wheelchair") was performed on 2011-05-10. A short video called "The Sighted Wheelchair" can be found on YouTube.Future work will focus on developing the software that communicates with the laser rangefinder and the haptic device to improve the user experience. Efforts will also be made to overcome the limitations of the laser rangefinder, improving the 3D model.

  • 7.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Fredriksson, Håkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Obstacle Avoidance Using Haptics and a Laser Rangefinder2013Inngår i: 2013 IEEE Workshop on Advanced Robotics and its Social Impacts: Tokya, Japan, 7-9 Nov 2013, Piscataway, NJ: IEEE Communications Society, 2013, s. 76-81Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In its current form, the white cane has been used by visually impaired people for almost a century. It is one of the most basic yet useful navigation aids, mainly because of its simplicity and intuitive usage. For people who have a motion impairment in addition to a visual one, requiring a wheelchair or a walker, the white cane is impractical, leading to human assistance being a necessity. This paper presents the prototype of a virtual white cane using a laser rangefinder to scan the environment and a haptic interface to present this information to the user. Using the virtual white cane, the user is able to "poke" at obstacles several meters ahead and without physical contact with the obstacle. By using a haptic interface, the interaction is very similar to how a regular white cane is used. This paper also presents the results from an initial field trial conducted with six people with a visual impairment.

  • 8.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Presentation of Spatial Information in Navigation Aids for the Visually Impaired2015Inngår i: Journal of Assistive Technologies, ISSN 1754-9450, E-ISSN 2042-8723, Vol. 9, nr 3, s. 174-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: The purpose of this article is to present some guidelines on how different means of information presentation can be used when conveying spatial information non-visually. The aim is to further the understanding of the qualities navigation aids for visually impaired individuals should possess.Design/methodology/approach: A background in non-visual spatial perception is provided, and existing commercial and non-commercial navigation aids are examined from a user interaction perspective, based on how individuals with a visual impairment perceive and understand space.Findings: The discussions on non-visual spatial perception and navigation aids lead to some user interaction design suggestions. Originality/value: This paper examines navigation aids from the perspective of non-visual spatial perception. The presented design suggestions can serve as basic guidelines for the design of such solutions.

  • 9.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Prellwitz, Maria
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Röding, Jenny
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Nyberg, Lars
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    An Initial Field Trial of a Haptic Navigation System for Persons with a Visual Impairment2015Inngår i: Journal of Assistive Technologies, ISSN 1754-9450, E-ISSN 2042-8723, Vol. 9, nr 4, s. 199-206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose– The purpose of this paper is to describe conceptions of feasibility of a haptic navigation system for persons with a visual impairment (VI). Design/methodology/approach– Six persons with a VI who were white cane users were tasked with traversing a predetermined route in a corridor environment using the haptic navigation system. To see whether white cane experience translated to using the system, the participants received no prior training. The procedures were video-recorded, and the participants were interviewed about their conceptions of using the system. The interviews were analyzed using content analysis, where inductively generated codes that emerged from the data were clustered together and formulated into categories. Findings– The participants quickly figured out how to use the system, and soon adopted their own usage technique. Despite this, locating objects was difficult. The interviews highlighted the desire to be able to feel at a distance, with several scenarios presented to illustrate current problems. The participants noted that their previous white cane experience helped, but that it nevertheless would take a lot of practice to master using this system. The potential for the device to increase security in unfamiliar environments was mentioned. Practical problems with the prototype were also discussed, notably the lack of auditory feedback. Originality/value– One novel aspect of this field trial is the way it was carried out. Prior training was intentionally not provided, which means that the findings reflect immediate user experiences. The findings confirm the value of being able to perceive things beyond the range of the white cane; at the same time, the participants expressed concerns about that ability. Another key feature is that the prototype should be seen as a navigation aid rather than an obstacle avoidance device, despite the interaction similarities with the white cane. As such, the intent is not to replace the white cane as a primary means of detecting obstacles.

  • 10.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Prellwitz, Maria
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Röding, Jenny
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Nyberg, Lars
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Virtuell vit käpp för den seende rullstolen2013Konferansepaper (Annet vitenskapelig)
  • 11.
    Ahlmark, Daniel Innala
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Hand-held navigation aid for visually impaired using haptic feedback2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The white cane is used by many visually impaired individuals as the primary aid for avoiding obstacles. In this it is unparalleled, but it cannot provide a large-scale view of the surroundings the way vision does. This makes navigating independently a challenge for the visually impaired. We are developing the Virtual White Cane (VWC), a device that uses sensors and haptic technologies to complement the limited view of the cane. Sensors makes it possible to probe obstacles far beyond the range of the white cane, and haptic feedback is familiar to users of the regular cane. The purpose of this device is to act as a complement to the standard cane, providing information about the surroundings that are beyond the cane's reach. This kind of extended view not only helps in anticipating obstacles, but also to navigate. The presentation will focus on the hardware of the currently developed prototype, in addition to some initial user experiences.

  • 12.
    Aitomäki, Yvonne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Online fibre property measurements: foundations for a method based on ultrasound attenuation2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents the foundations of a method for estimating fibre properties of pulp suitable for online application in the pulp and paper industry. In the pulp and paper industry, increased efficiency and greater paper quality control are two of the industry's main objectives. It is proposed that online fibre property measurements are a means of achieving progress in both of these objectives. Optical based systems that provide valuable geometric data on the fibres and other pulp characteristics are commercially available. However, measurements of the elastic properties of the fibres are not currently implemented using these systems. To fill this gap an ultrasound based system for measuring the elastic properties of the wood fibres in pulp is proposed. Ultrasound propagation depends on the elastic properties of a solid. Hence attenuation measurements from suspensions of fibres depend on their elastic properties. The method is based on solving the inverse problem where the output is known and the objective is to establish the inputs. In this case, attenuation is measured and a model of attenuation based on ultrasound scattering is developed. A search algorithm is used for finding elastic properties that minimize the error between the model and measured attenuation. The results of the search are estimates of the elastic properties of the fibres in suspension. The results show resonance peaks in the attenuation, in the frequency region tested, for fibres with radii of the order of 10 microns. These peaks are found in both the measured and modelled attenuation spectra. Further investigation of these resonances suggests that they are due to modes of vibration in the fibre where the fibre modelled as an infinitely long cylinder. These resonances are shown to aid in the identification of the elastic properties. The attenuation is found to depend heavily on the geometry of the fibres. Hence fibre geometry, which can be obtained from online optical fibre measurement system, provides the key to extracting the elastic properties from the attenuation signal. Studies are also carried out on the effect of viscosity on attenuation as well as the differences in attenuation between hollow and solid synthetic fibres in suspensions. The measurement method is also applied to hardwood and softwood Kraft pulps. The results of these studies show that using the model derived in the thesis and attenuation measurements, estimates of the elastic properties can be obtained. The elastic property estimates for synthetic fibres agree well with values from other methods. The elastic property estimates for pulps require further validation due to the difficulty in comparing between different testing methods and different types of pulp. The conclusions, based on the work so far and under three realisable conditions, are that the shear modulus and the transverse Young's modulus of pulp fibres can be measured. Once these conditions are met a system based on this method can be implemented. By doing this the industry would benefit from the increase in paper quality control and energy saving such system could provide.

  • 13.
    Aitomäki, Yvonne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Towards a measurement of paper pulp quality: ultrasonic spectroscopy of fibre suspensions2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For the paper and pulp industry in Sweden and Finland to remain competitive against countries with lower overheads, they have to constantly strive to improve the quality and the efficiency of the manufacturing processes. One of the ways of doing this is to introduce sensors that will provide valuable online feedback on the characteristics of the pulp so that adjustments can be made to optimise the manufacturing process. The measurement method proposed in this thesis is based on ultrasound, since it is rapid, inexpensive, non-destructive and non-intrusive. Thus could be done online. Since ultrasound propagation and attenuation depends on the material properties through which is propagates, it has the potential to provide measurements of material properties such as pulp fibre density and elasticity. The aim of this thesis is to investigate the possibility of using ultrasound to measure pulp fibre material properties. The idea is to solve the inverse problem of estimating these properties from attenuation measurements and to establish the degree of accuracy to which this can be done. Firstly a model is developed and is tested with synthetic fibres to establish is validity. It is then used to solve the inverse problem of estimating material properties from attenuation measurements, again with synthetic fibres, to test the accuracy to which these properties can be estimated. Resonance peaks in the frequency response of the attenuation were found. On closer investigation it was established that the location of these peaks in the frequency domain is sensitive to the diameter of the fibres and their material properties. If the diameter is known, these peaks improve the accuracy of the estimation process. The results of the estimation process for synthetic fibre suspensions show values for the shear modulus are within known ranges but the estimation of Poisson's ratio and Young's modulus is poor. Improving the model or the estimation procedure may lead to better results. For the method as it is to have application in the paper and pulp industry there are certain conditions that need to be fulfilled. These are that we find peaks in the frequency response of the attenuation in pulp, know the diameter distribution of the fibres and the hollow nature of the fibres does not significantly alter the results. We can then, potentially, be able to establish the shear modulus of the pulp fibres. If the shear modulus is a factor in paper quality, we may be close to an online measurement of paper pulp quality using ultrasonic spectroscopy. Improving the model may allow us to estimate further properties and take into account the fibres being hollow. The thesis consists of two parts. The first part includes an overview of the pulp and paper industry and current testing methods, background theory on which the model is based and an overview of the model that is used in predicting ultrasound attenuation. There then follows a summary of the work done, some addition points are raised in the discussion before drawing conclusions. Finally we discuss what needs to be done to take this further. The second part contains a collection of four papers describing the research.

  • 14.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Noël, Maxime
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Linder, Tomas
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Light scattering in cellulose nanofibre suspensions: Model and experiments2016Inngår i: Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego, American Chemical Society (ACS), 2016, s. 122-, artikkel-id CELL 235Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.

  • 15. Aitomäki, Yvonne
    et al.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Estimating suspended fibre material properties by modelling ultrasound attenuation2006Inngår i: Mathematical Modeling of Wave Phenomena: conference on mathematical modeling of wave phenomea, Växjö, Sweden, 14 - 19 August 2005 / [ed] Börje Nilsson; Louis Fishman, Melville, NY: American Institute of Physics (AIP), 2006, s. 250-259Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An analytical model for use in the inverse problem of estimating material properties of suspended fibres from ultrasonic attenuation has been developed. The ultrasound attenuation is derived theoretically from the energy losses arising when a plane wave is scattered and absorbed off an infinitely long, isotropic, viscoelastic cylinder. By neglecting thermal considerations and assuming low viscosity in the suspending fluid, we can make additional assumptions that provide us with a tractable set of equations that can be solved analytically. The model can then be to used in inverse methods of estimating material properties. We verify the model with experimentally obtained values of attenuation for saturated Nylon fibres. The experimental results from Nylon fibres show local peaks in the attenuation which are thought to be due to the resonant absorption at the eigenfrequencies of the fibres. The results of the experiments show that the model is sufficiently sensitive to detect differences in different types of Nylon. Applications for suspended fibre characterization can be found in the paper manufacturing industry.

  • 16. Aitomäki, Yvonne
    et al.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Material property estimates from ultrasound attenuation in fibre suspensions2009Inngår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 49, nr 4-5, s. 432-437Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation of a new method for measuring fibre material properties from ultrasonic attenuation in a dilute suspension of synthetic fibres of uniform geometry is presented. The method is based on inversely solving an ultrasound scattering and absorption model of suspended fibres in water for the material properties of the fibres. Experimental results were obtained from three suspensions of nylon 66 fibres each with different fibre diameters. A forward solution to the model with reference material values is compared to experimental data to verify the model's behaviour. Estimates of the shear and Young's modulus, the compressional wave velocity, Poisson's ratio and loss tangent from nylon 66 fibres are compared to data available from other sources. Experimental data confirms that the model successfully predicts that the resonance features in the frequency response of the attenuation are a function of diameter. Consistent estimated values for the compressional wave velocity and the Poisson's ratio were found to be difficult to obtain but in combination gave values of shear modulus within previously reported values and with low sensitivity to noise. Young's modulus was underestimated by 54% but was consistent and had low sensitivity to noise. The underestimation is believed to be caused by the assumption of isotropic material used in the model. Additional tests on isotropic fibre would confirm this. Further analysis of the model sensitivity and the reasons for the resonance features are required.

  • 17.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Sounding Out Paper Pulp: Ultrasound Spectroscopy of Dilute Viscoelastic Fibre Suspensions Acoustics and Ultrasonics2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A model of attenuation of ultrasound in fibre suspensions is compared to a model of backscattering pressure from submersed cylinders subjected to a sound wave. This analysis is carried out in the region where the wavelength is of the same order as that of the diameter of the fibre. In addition we assume the cylinder scatterer to have no intrinsic attenuation and the longitudinal axis of the scatterer is assumed to be perpendicular to the direction of propagation of the incident wave. Peaks in the frequency response of both the backscattering pressure, expressed in the form of a form function, and the attenuation are shown to correspond. Similarities between the models are discussed. Since the peaks in the form function are due to resonance of the cylinder, we infer that the peaks in the attenuation are also due to resonance. The exact nature of the waves causing the resonance are still unclear however the first resonance peaks are related to the shear wave and hence the shear modulus of the material. The aim is to use the attenuation model for solving the inverse problem of calculating paper pulp material properties from attenuation measurements. The implications of these findings for paper pulp property estimation is that the supporting fluid could, if possible, be matched to density of that of pulp fibres and that the estimation of material properties should be improved by selecting a frequency range that in the region of the first resonance peaks.

  • 18.
    Aitomäki, Yvonne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation2013Inngår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 60, nr 7, s. 1424-1434Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Estimates of the material properties of hollow fibers suspended in a fluid using ultrasound measurements and a simple, computationally efficient analytical model are made. The industrial application is to evaluate the properties of wood fibers in paper pulp. The necessity of using a layered cylindrical model (LCM) as opposed to a solid cylindrical model (SCM) for modeling ultrasound attenuation in a suspension of hollow fibers is evaluated. The two models are described and used to solve the inverse problem of estimating material properties from attenuation in suspensions of solid and hollow polyester fibers. The results show that the measured attenuation of hollow fibers differs from that of solid fibers. Elastic properties estimates using LCM with hollow-fiber suspension measurements are similar to those using SCM with solid-fiber suspension measurements and compare well to block polyester values for elastic moduli. However, using the SCM with the hollow-fiber suspension did not produce realistic estimations. In conclusion, the LCM gives reasonable estimations of hollow fiber properties and the SCM is not sufficiently complex to model hollow fibers. The results also indicate that the use of a distributed radius in the model is important in estimating material properties from fiber suspensions.

  • 19.
    Aittamaa, Simon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Programming embedded real-time systems: implementation techniques for concurrent reactive objects2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    An embedded system is a computer system that is a part of a larger device with hardware and mechanical parts. Such a system often has limited resources (such as processing power, memory, and power) and it typically has to meet hard real-time requirements. Today, as the area of application of embedded systems is constantly increasing, resulting in higher demands on system performance and a growing complexity of embedded software, there is a clear trend towards multi-core and multi-processor systems. Such systems are inherently concurrent, but programming concurrent systems using the traditional abstractions (i.e., explicit threads of execution) has been shown to be both difficult and error-prone. The natural solution is to raise the abstraction level and make concurrency implicit, in order to aid the programmer in the task of writing correct code. However, when we raise the abstraction level, there is always an inherent cost. In this thesis we consider one possible concurrency model, the concurrent reactive object approach that offers implicit concurrency at the object level. This model has been implemented in the programming language Timber, which primarily targets development of real-time systems. It is also implemented in TinyTimber, a subset of the C language closely matching Timber’s execution model. We quantify various costs of a TinyTimber implementation of the model (such as context switching and message passing overheads) on a number of hardware platforms and compare them to the costs of the more common thread-based approach. We then demonstrate how some of these costs can be mitigated using stack resource policy. On a separate track, we present a feasibility test for garbage collection in a reactive real-time system with automatic memory management, which is a necessary component for verification of correctness of a real-time system implemented in Timber

  • 20.
    Aittamaa, Simon
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Eriksson, Johan
    Lindgren, Per
    Uniform scheduling of internal and external events under SRP-EDF2010Inngår i: Annual International Conference on Real-Time and Embedded Systems ( RTES 2010): 1-2 November 2010, Mandarin Orchard Hotel, Singapore, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With the growing complexity of modern embedded real-time systems, scheduling and managing of resources has become a daunting task. While scheduling and resource management for internal events can be simplified by adopting a commonplace real-time operating system (RTOS), scheduling and resource management for external events are left in the hands of the programmer, not to mention managing resources across the boundaries of external and internal events. In this paper we propose a unified system view incorporating earliest deadline first (EDF) for scheduling and stack resource policy (SRP) for resource management. From an embedded real-time system view, EDF+SRP is attractive not only because stack usage can be minimized, but also because the cost of a pre-emption becomes almost as cheap as a regular function call, and the number of preemptions is kept to a minimum. SRP+EDF also lifts the burden of manual resource management from the programmer and incorporates it into the scheduler. Furthermore, we show the efficiency of the SRP+EDF scheme, the intuitiveness of the programming model (in terms of reactive programming), and the simplicity of the implementation.

  • 21.
    Akos, Dennis
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ene, A.
    Stanford University.
    Thor, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    A prototyping platform for multi-frequency GNSS receivers2003Inngår i: ION GPS/GNSS Proceedings, Institute of Navigation, The , 2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The future satellite positioning/navigation systems (i.e. GPS and Galileo) will provide civil signals on multiple frequencies, similar to those currently available for military purposes only. This paper presents a direct RF sampling front end design well suited for multiple frequency satellite navigation receiver design. No frequency downconversion is necessary; rather the particular frequency bands of interest are intentionally aliased using a wide band analog-to-digital converter (ADC). The resulting samples are passed to the memory space of a host PC for storage, and are saved to disk for eventual processing of the multiple frequency transmissions. The present paper describes the design of the front-end, validates its concept with collected data, and discusses the variations on the design of a generic multiple frequency GPS front end. Methods for processing the data obtained by the front end design are also presented.

  • 22.
    Akos, Dennis
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    From, Markus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Karlsson, Mattias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Larsson, Kjell
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Receiver measured time in the VDL mode 4 system2000Inngår i: IEEE 2000 Position Location and Navigation Symposium: San Diego, California, March 13 - 16, 2000, Piscataway, NJ: IEEE Communications Society, 2000, s. 309-316Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper details an investigation into the receiver measured time (RMT) concept of VDL Mode 4, basically the ability to derive estimates of time from the transmission of the VDL Mode 4 signals themselves. The RMT concept is based on determining the accurate time of transmission by measuring the time of arrival (TOA) of a received signal. The reverse aspect, or that of user position, can also be computed in the same manner and all computed simulations hold for errors in position. If synchronized time is available, or can be derived, then the user position can be computed based on signals from known transmitter locations. A complete, end-to-end RMT simulation model for the Gaussian filtered frequency shift keying (GFSK) and differential 8-phase shift keying (D8PSK) modulation techniques has been developed in which various transmitters, channels and receiver models as well as an RMT measurement system have been included. The timing results, which are included, are described in terms of two-sigma errors as a function of signal-to-noise ratios (SNRs). The performance varies for the different receiver structures over the typical operation region and for a 1-bit differential GFSK detector the two-sigma error is as low as 0.40 microseconds, corresponding to a ranging error of approximately 120 meters. When incorporating co-channel interference (CCI), multipath and Doppler frequency shifts the RMT performance has been shown to decrease in terms of higher two-sigma errors

  • 23.
    Akos, Dennis
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Stockmaster, Michael
    Rockwell Collins, Cedar Wells.
    Tsui, James B.Y.
    Wright-Patterson Air Force Base, Dayton.
    Caschera, Joe
    Wright-Patterson Air Force Base, Dayton.
    Direct bandpass sampling of multiple distinct RF signals1999Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 47, nr 7, s. 983-988Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A goal in the software radio design philosophy is to place the analog-to-digital converter as near the antenna as possible. This objective has been demonstrated for the case of a single input signal. Bandpass sampling has been applied to downconvert, or intentionally alias, the information bandwidth of a radio frequency (RF) signal to a desired intermediate frequency. The design of the software radio becomes more interesting when two or more distinct signals are received. The traditional approach for multiple signals would be to bandpass sample a continuous span of spectrum containing all the desired signals. The disadvantage with this approach is that the sampling rate and associated discrete processing rate are based on the span of spectrum as opposed to the information bandwidths of the signals of interest. Proposed here is a technique to determine the absolute minimum sampling frequency for direct digitization of multiple, nonadjacent, frequency bands. The entire process is based on the calculation of a single parameter-the sampling frequency. The result is a simple, yet elegant, front-end design for the reception and bandpass sampling of multiple RF signals. Experimental results using RF transmissions from the US Global Positioning System-Standard Position Service (GPS-SPS) and the Russian Global Navigation Satellite System (GLONASS) are used to illustrate and verify the theory

  • 24.
    Albano, Michele
    et al.
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Barbosa, Paulo Miguel
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Silva, Jose
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Duarte, Roberto
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Ferreira, Luis Lino
    CISTER, ISEP/INESC-TEC Polytechnic Institute of Porto.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Quality of Service on the Arrowhead Framework2017Inngår i: 2017 IEEE 13th International Workshop on Factory Communication Systems (WFCS), Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, artikkel-id 7991959Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Quality of Service (QoS) is an important enabler for communication in industrial environments. The Arrowhead Framework was created to support local cloud functionalities for automation applications by means of a Service Oriented Architecture. To this aim, the framework offers a number of services that ease application development, among them the QoSSetup and the Monitor services, the first used to verify and configure QoS in the local cloud, and the second for online monitoring of QoS. This paper describes how the QoSSetup and Monitor services are provided in a Arrowhead-compliant System of Systems, detailing both the principles and algorithms employed, and how the services are implemented. Experimental results are provided, from a demonstrator built over a real-time Ethernet network.

  • 25.
    Alberti, M.
    et al.
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Switzerland.
    Pondenkandath, V.
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Switzerland.
    Wursch, M.
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Switzerland.
    Ingold, R.
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Switzerland.
    Liwicki, Marcus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB. Document Image and Voice Analysis Group (DIVA), University of Fribourg, Switzerland.
    DeepDIVA: A Highly-Functional Python Framework for Reproducible Experiments2018Inngår i: Proceedings of International Conference on Frontiers in Handwriting Recognition, ICFHR 2018, IEEE, 2018, s. 423-428, artikkel-id 8583798Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We introduce DeepDIVA: an infrastructure designed to enable quick and intuitive setup of reproducible experiments with a large range of useful analysis functionality. Reproducing scientific results can be a frustrating experience, not only in document image analysis but in machine learning in general. Using DeepDIVA a researcher can either reproduce a given experiment or share their own experiments with others. Moreover, the framework offers a large range of functions, such as boilerplate code, keeping track of experiments, hyper-parameter optimization, and visualization of data and results. To demonstrate the effectiveness of this framework, this paper presents case studies in the area of handwritten document analysis where researchers benefit from the integrated functionality. DeepDIVA is implemented in Python and uses the deep learning framework PyTorch. It is completely open source(1), and accessible as Web Service through DIVAServices(2).

  • 26.
    Alberti, Michele
    et al.
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Pondenkandath, Vinaychandran
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Würsch, Marcel
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Bouillon, Manuel
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Seuret, Mathias
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Ingold, Rolf
    Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Liwicki, Marcus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB. Document Image and Voice Analysis Group (DIVA), University of Fribourg, Fribourg, Switzerland.
    Are You Tampering with My Data?2019Inngår i: Computer Vision – ECCV 2018 Workshops: Proceedings, Part II / [ed] Laura Leal-Taixé & Stefan Roth, Springer, 2019, s. 296-312Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a novel approach towards adversarial attacks on neural networks (NN), focusing on tampering the data used for training instead of generating attacks on trained models. Our network-agnostic method creates a backdoor during training which can be exploited at test time to force a neural network to exhibit abnormal behaviour. We demonstrate on two widely used datasets (CIFAR-10 and SVHN) that a universal modification of just one pixel per image for all the images of a class in the training set is enough to corrupt the training procedure of several state-of-the-art deep neural networks, causing the networks to misclassify any images to which the modification is applied. Our aim is to bring to the attention of the machine learning community, the possibility that even learning-based methods that are personally trained on public datasets can be subject to attacks by a skillful adversary.

  • 27.
    Albertsson, Kim
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Gleyzer, Sergei
    University of Florida.
    Zapata, Omar
    OProject and University of Antioquia.
    Machine Learning in High Energy Physics Community White Paper2018Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 1085, artikkel-id 022008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Machine learning is an important applied research area in particle physics, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle and event identification and reconstruction in the 2010s. In this document we discuss promising future research and development areas in machine learning in particle physics with a roadmap for their implementation, software and hardware resource requirements, collaborative initiatives with the data science community, academia and industry, and training the particle physics community in data science. The main objective of the document is to connect and motivate these areas of research and development with the physics drivers of the High-Luminosity Large Hadron Collider and future neutrino experiments and identify the resource needs for their implementation. Additionally we identify areas where collaboration with external communities will be of great benefit.

  • 28.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hajlane, Abdelghani
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Renbi, Abdelghani
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ouarga, Ayoub
    Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Chouhan, Shailesh Singh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Conductive Regenerated Cellulose Fibers by Electroless Plating2019Inngår i: Fibers, ISSN 2079-6439, Vol. 7, nr 5, artikkel-id 38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Continuous metallized regenerated cellulose fibers for advanced applications (e.g. multi-functional composites) are produced by electroless copper plating. Copper is successfully deposited on the surface of cellulose fibers using commercial cyanide-free electroless copper plating package commonly available for manufacturing of printed wiring boards. The deposited copper is found to enhance the thermal stability, electrical conductivity and resistance to moisture uptake of the fibers. On the other hand, involved chemistry results in altering the molecular structure of the fibers as is indicated by the degradation of their mechanical performance (tensile strength and modulus).

  • 29. Alrifaiy, Ahmed
    et al.
    Borg, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A lab-on-a-chip for hypoxic patch clamp measurements combined with optical tweezers and spectroscopy: first investigations of single biological cells2015Inngår i: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 14, artikkel-id 36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The response and the reaction of the brain system to hypoxia is a vital research subject that requires special instrumentation. With this research subject in focus, a new multifunctional lab-on-a-chip (LOC) system with control over the oxygen content for studies on biological cells was developed. The chip was designed to incorporate the patch clamp technique, optical tweezers and absorption spectroscopy. The performance of the LOC was tested by a series of experiments. The oxygen content within the channels of the LOC was monitored by an oxygen sensor and verified by simultaneously studying the oxygenation state of chicken red blood cells (RBCs) with absorption spectra. The chicken RBCs were manipulated optically and steered in three dimensions towards a patch-clamp micropipette in a closed microfluidic channel. The oxygen level within the channels could be changed from a normoxic value of 18% O 2 to an anoxic value of 0.0-0.5% O 2. A time series of 3 experiments were performed, showing that the spectral transfer from the oxygenated to the deoxygenated state occurred after about 227 ± 1 s and a fully developed deoxygenated spectrum was observed after 298 ± 1 s, a mean value of 3 experiments. The tightness of the chamber to oxygen diffusion was verified by stopping the flow into the channel system while continuously recording absorption spectra showing an unchanged deoxygenated state during 5400 ± 2 s. A transfer of the oxygenated absorption spectra was achieved after 426 ± 1 s when exposing the cell to normoxic buffer. This showed the long time viability of the investigated cells. Successful patching and sealing were established on a trapped RBC and the whole-cell access (Ra) and membrane (Rm) resistances were measured to be 5.033 ± 0.412 M Ω and 889.7 ± 1.74 M Ω respectively.

  • 30.
    Andersson, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    EMC robot1997Rapport (Annet vitenskapelig)
  • 31.
    Andersson, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Analysis of 3D surface data for on-line determination of the size distribution of iron ore pellet piles on conveyor belt2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Size measurement of iron ore pellets in industry is usually performed by manual sampling and sieving techniques. The manual sampling is performed infrequently and is inconsistent, invasive and time-consuming. Iron ore pellet's sizes are critical to the efficiency of the blast furnace process in the production of steel. Overly coarse pellets affect the blast furnace process negatively, however this affect can be minimized by operating the furnace with different parameters. An on-line system for measurement of pellet sizes would improve productivity through fast feedback and efficient control of the blast furnace. Also, fast feedback of pellet sizes would improve pellet quality in pellet production. Image analysis techniques promise a quick, inexpensive, consistent and non-contact solution to determining the size distribution of a pellet pile. Such techniques capture information of the surface of the pellet pile which is then used to infer the pile size distribution. However, there are a number of sources of error relevant to surface analysis techniques. The objective of this thesis is to address and overcome aspects of these sources of error relevant to surface analysis techniques. The research problem is stated as: How can the pellet pile size distribution be estimated with surface analysis techniques using image analysis? This problem is addressed by dividing the problem into sub-problems. The focus of the presented work is to develop techniques to overcome, or minimize, two of these sources of error; overlapped particle error and profile error. Overlapped particle error describes the fact that many pellets on the surface of a pile are only partially visible and a large bias results if they are sized as if they were smaller entirely visible pellets. No other researchers make this determination. Profile error describes the fact that only one side of an entirely visible pellet can be seen making it difficult to estimate pellets size. Statistical classification methods are used to overcome these sources of error. The thesis is divided into two parts. The first part contains an introduction to the research area together with a summary of the contributions, and the second part is a collection of four papers describing the research.

  • 32.
    Andersson, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Bortolin, Gianantonio
    Volvo CE.
    Backén, Staffan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Estimation of side-slip angles of a Volvo A25E articulated all-wheel drive hauler based on GPS/INS measurements2011Inngår i: Proceedings of SAE 2011 Commercial Vehicle Engineering Congress and Exhibition, Society of Automotive Engineers, Incorporated , 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Traction control for off-road vehicles such as articulated all-wheel drive haulers is of great importance to improve the vehicle performance. A well-known method to reduce the slip and thereby improve the traction is to engage differential locks in the driveline of the vehicle. The drawbacks of differential locks engaged are for instance increased wear, increased fuel consumption but also reduced turnability of the vehicle. Therefore, the differentials should be locked only when necessary, ideally only when slip occurs or is about to occur. A number of methods to detect slip has been reported in the literature. Some of them utilize dynamical models of the vehicle where side-slip angles are important inputs. This paper describes an off-line estimator for the side-slip angles of an articulated vehicle based on measurements from Global Positioning System (GPS) and Inertial Navigation System (INS). The current implementation is a proof of concept and the intention is to develop a system that can be used as a reference for on-line estimators. By comparing measurements from two GPS/INS units, mounted on the front and rear part of the vehicle, it is possible to estimate the side-slip angles of both the front and rear part. The method has been tested on a Volvo A25E articulated all-wheel drive hauler equipped with two high precision GPS/INS units (NovAtel's SPAN-CPT). Tests have been performed when driving on asphalt, gravel and snow. The results from the tests are discussed.

  • 33.
    Andersson, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mrozek, Kent
    Åström, Kalle
    Hyyppä, Kalevi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Path design and control algorithms for articulated mobile robots1997Inngår i: Proceedings of the International Conference on Field and Service Robotics / [ed] Alexander Zelinsky, 1997, s. 405-411Konferansepaper (Fagfellevurdert)
  • 34. Antonini, G.
    et al.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ruehli, A.E.
    Accuracy and stability enhancement of PEEC models for the time and frequency domain2006Inngår i: EMC Europe 2006 Barcelona: [International Symposium on Electromagnetic Compatibility ; September 4 - 8, 2006, Barcelona, Spain] / [ed] Ferran Silva, Barcelona: Universidad Politécnica de Cataluña , 2006Konferansepaper (Fagfellevurdert)
  • 35.
    Antonini, G.
    et al.
    Università Degli Studi di l'Aquila.
    Miscione, G.
    Università Degli Studi di l'Aquila.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    PEEC modeling of automotive electromagnetic problems2008Inngår i: Applied Computational Electromagnetics Society Newsletter, ISSN 1056-9170, Vol. 23, nr 1, s. 39-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the combination of the nonorthogonal Partial Element Equivalent Circuit (PEEC) models and interconnect structures through a macromodel approach for the analysis of automotive electromagnetic problems. The applications are within automotive computational electromagnetics due to the typical combination of cable harnesses and chassis structures. It is shown that PEEC-based solvers are capable of handling electrically large problems with high geometrical complexity for detailed analysis in both the time- and frequency- domain with attached multi-conductor transmission lines.

  • 36. Antonini, G.
    et al.
    Miscione, G.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Anttu, Peter
    PEEC modeling of automotive electromagnetic problems2006Inngår i: Proceedings of the International Conference of Numerical Analysis and Applied Mathematics: official conference European Society of Computational Methods in Sciences and Engineering (ESCMSE) / [ed] T. E. Simos, John Wiley & Sons, 2006Konferansepaper (Fagfellevurdert)
  • 37.
    Antonini, Giulio
    et al.
    University of L'Aquila (Italy).
    De Lauretis, Maria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Miroshnikova, Elena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On the passivity of the Delay-Rational Green’s-function-based model for Transmission Lines2019Inngår i: Analysis, Probability, Applications, and Computation: Proceedings of the 11th ISAAC Congress / [ed] Karl‐Olof Lindahl,Torsten Lindström, Luigi G. Rodino, Joachim Toft, Patrik Wahlberg, 2019, s. 71-81Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we study the delay-rational Green’s-function-based (DeRaG) model for transmission lines. This model is described in terms of impedance representation and it contains a rational and a hyperbolic part. The crucial property of transmission lines models is to be passive. The passivity of the rational part has been studied by the authors in a previous work. Here, we extend the results to the rational part of the DeRaG model. Moreover, we prove the passivity of the hyperbolic part. 

  • 38.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Orlandi, Antonio
    Department of Electrical Engineering, University of L’Aquila.
    Ruehli, Albert
    IBM T.J. Watson Research Center, Yorktown Heights.
    PEEC development road map 20072007Rapport (Annet vitenskapelig)
    Abstract [en]

    A road map for the long term development of the partial element equivalent circuit (PEEC) method is presented. Emerging areas are pointed out together with a solution strategy. Special attention is given to speed up approaches, mesh generation, and time domain stability. The purpose with the road map is to facilitate a unified development of the method into an electromagnetic modeling method suitable for incorporation in integrated analysis tools for engineers for electromagnetic compatibility and electromagnetic interference purpose.

  • 39.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ruehli, Albert
    IBM T.J. Watson Research Center, Yorktown Heights.
    Parallel waveform relaxation and matrix solution for large PEEC model problems2007Inngår i: 2007 IEEE Electrical Performance of Electronic Packaging, IEEE Communications Society, 2007, s. 241-244Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Excessive compute time is becoming a key problem for high performance system modeling as the complexity of the electromagnetic and circuit models are increasing. At the same time the PEEC models are locally becoming more complex with the increased importance of dielectric and skin-effect losses. Fortunately, parallel processing removes the restriction on the availability of compute resources. In this paper,we consider a combined approach where WR is used for the predominant weak coupling while a Gaussian matrix solver is used for the parallelization of the strongly coupled parts of the overall system.

  • 40.
    Antonini, Giulio
    et al.
    Department of Electrical Engineering, University of L’Aquila.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ruehli, Albert E.
    IBM T.J. Watson Research Center, Yorktown Heights.
    Waveform relaxation for the parallel solution of large PEEC model problems2007Inngår i: 2007 IEEE International Symposium on Electromagnetic Compatibility: workshop and tutorial notes : July 8-13, 2007 Honolulu, Hawaii., Piscataway, NJ: IEEE Communications Society, 2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The solution of large 3D electromagnetic models is important for the modeling of a multitude of EMC, PI and SI problems. In this paper, we explore new algorithms for the parallel solution of large time domain 3D electromagnetic problems. Our approach is to use a volume Partial Element Equivalent Circuit (PEEC) electromagnetic formulation in combination with a Waveform Relaxation (WR) algorithm. In WR, we split the system into smaller subsystems and we break weak couplings so that the problem can be solved iteratively. WR has been used to solve a multitude of different problems. It is especially suited for parallel processing due to its favorable compute time to communication ratio. We consider a specific example for the application of WR to PEEC models.

  • 41.
    Antonini, Giulio
    et al.
    University of L’Aquila.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Scogna, Antonio Ciccomancini
    University of L’Aquila.
    Ruehli, Albert E.
    IBM Research Division, Yorktown Heights, NY.
    A comparative study of PEEC circuit elements computation2003Inngår i: IEEE International Symposium on Electromagnetic Compatibility: symposium record : Boston, August 18-22, 2003, Piscataway, NJ: IEEE Communications Society, 2003, s. 810-813Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A key use of the PEEC method is the solution of combined electromagnetic and circuit problems as they occur in many situations in todays very large scale integrated circuits (VLSI) and systems. An important aspect of this approach is the fast and accurate computation of PEEC circuit matrix elements, the partial inductances and normalized coefficients of potential. Recently, fast multipole methods (FMM) have been applied to the PEEC method in the frequency domain as a way to speed up the solution. In this paper, we consider the fast evaluation of the PEEC circuit matrix elements by two different methods, a matrix version of the (FMM) PEEC method and a method, which we call the fast multi-function (FMF) PEEC approach. In this technique, the matrix coefficients are evaluated using analytical functions approximation of the coefficients in combination with a proper choice of numerical quadrature formulas.

  • 42.
    Aparicio Rivera, Jorge
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Lindner, Marcus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB. Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Lindgren, Per
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB. Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Heapless: Dynamic Data Structures without Dynamic Heap Allocator for Rust2018Inngår i: 2018 IEEE 16TH INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS (INDIN), Piscataway, NJ: IEEE, 2018, s. 87-94, artikkel-id 8472097Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dynamic memory management is typically implemented using a global memory allocator, which may negatively impact the performance, reliability, and predictability of a program; in effect standards around safety-critical applications often discourage or even disallow dynamic memory management. This paper presents heapless, a collection of dynamic data structures (for vectors, strings, and circular buffers) that can be either stack or statically allocated, thus free of global allocator dependencies. The proposed data structures for vectors and strings closely mimic the Rust standard library implementations while adding support to gracefully handling cases of capacity exceedance. Our circular buffers act as queues and allowing channel like usage (by splitting). The Rust memory model together with the ability of local reasoning on memory requirements (brought by heapless) facilitates establishing robustness/safety guarantees and minimize attack surfaces of (industrial) IoT systems. We show that the heapless data structures are highly efficient and have predictable performance, thus suitable for hard real-time applications. Moreover, in our implementation heapless data structures are non-relocatable allowing mapping to hardware, useful, e.g., to DMA transfers. The feasibility, performance, and advantages of heapless are demonstrated by implementing a JSON serialization and de-serialization library for an ARM Cortex-M based IoT platform.

  • 43.
    Axell, Erik
    et al.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Eklöf, Fredrik M.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Alexandersson, Mikael
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Johansson, Peter
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Akos, Dennis
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Jamming detection in GNSS receivers: Performance evaluation of field trials2013Inngår i: Proceedings of the 26th international technical meeting of the Satellite Division of The Institute of Navigation, ION GNSS+ 2013, Sept. 16 - 20, 2013, Nashville Convention Cener, Nashville, Tennessee, Manassas, VA: Institute of Navigation, The , 2013, Vol. 3, s. 2542-2551Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work, we evaluate the detection performance of a number of commercial interference detectors and, in addition, of a detector that uses the automatic gain control (AGC) levels as test statistic. The AGC detector has been implemented on a Novatel GPS receiver and on a Universal Software Radio Peripheral (USRP). The evaluations are based on actual measurements of GPS signals and different types of jamming signals, which have been performed at the Vidsel test range in northern Sweden. The AGC detector was shown to work well for all types of jamming signals, in particular the one implemented on the USRP. The Chronos CTL-3500 was also shown to perform quite well for all kinds of signals, although not as good as the USRP with an AGC detector. Quite surprisingly, the J-alert was only able to detect the wideband (20 MHz) signal but not the narrow band (<2MHz) signals. By contrast, the jamming indicator on the Ublox 6 receiver was only able to detect a slowly varying modulated CW (MCW) signal, but not the signals with larger bandwidth (2 and 20 MHz). We confirmed that C/N0-based detectors could work well in a static scenario, but are not suitable in a dynamic scenario, since they cannot distinguish between decreased GPS signal strength (e.g. indoors) and an increased interference level.

  • 44.
    Axell, Erik
    et al.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Eklöf, Fredrik M.
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Alexandersson, Mikael
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Johansson, Peter
    Swedish Defence Research Agency, Department of Robust Telecommunications.
    Akos, Dennis
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Jamming detection in GNSS receivers: Performance evaluation of field trials2015Inngår i: Navigation, ISSN 0028-1522, E-ISSN 2161-4296, Vol. 62, nr 1, s. 73-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We evaluate the detection performance of several commercial interference detectors and of a detector that uses the automatic gain control (AGC) level as a test statistic. The evaluations are based on actual measurements of GPS signals and different types of jamming signals, and were performed at the Vidsel test range in northern Sweden.The AGC detector and the Chronos CTL-3500 were shown to work well for all types of jamming signals. The J-alert was able to detect a wideband (20 MHz) signal but not the narrow band (<2 MHz) signals. By contrast, the jamming indicator on a Ublox 6H receiver was only able to detect a slowly varying modulated CW signal, but not signals with larger bandwidth (>2 MHz). We confirmed that C/N0-based Android application detectors could work well in static scenarios but are not suitable in dynamic scenarios, since they cannot distinguish between decreased GPS signal strength and increased interference

  • 45.
    Backén, Staffan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Likelihood of detection and computational complexity of GPS acquisition algorithms2009Inngår i: Proceedings of the 22nd international technical meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2009: Sept. 22 - 25, 2009, Savanna Convention Center, Savannah, Georgia, Manassas, Va: Institute of Navigation, The , 2009, s. 3153-3160Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A key parameter of GNSS receiver performance is the sensitivity, meaning how weak signals the receiver can acquire and track. For acquisition, this is typically measured by the minimum signal strength that can be detected with a certain probability. In this paper, a novel method of computing the probability of detection is presented. In contrast with prevailing techniques, it takes receiver parameters such as correlator and doppler spacing into account when computing the probability distribution function. The likelihood of data bit switches inside the correlation window is also considered in a similar fashion. The method is demonstrated both on a traditional correlator architecture, and on two different FFT based acquisition algorithms, coherent and non-coherent. Further, the computational complexity of the different algorithms is evaluated for a general computing platform. The combination of these two methods provide valuable insight into the problem of minimizing power consumption while maximizing sensitivity for software based GNSS receivers.

  • 46.
    Backén, Staffan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    On dynamic array processing for GNSS software receivers2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents contributions in the field of satellite navigation with a focus on array processing and related implementation issues. For readers not familiar with GNSS, it also includes a brief overview of satellite navigation.Compared to the state of the art only ten years ago, modern GNSS receivers are very capable. One reason for this improvement is advances in the semiconductor industry that have increased both the available processing power and the energy efficiency. An active research community have also made important contributions resulting in more sophisticated algorithms. To improve receiver performance even further, auxiliary sensors such as gyros and accelerometers are becoming increasingly common. A related option involves using an antenna with several physical elements. This is known as an antenna array and is often used for radar, sonar and telecommunication applications. Array processing can also be used for GNSS and as such it is the primary focus of this thesis. An array allows for exploration of the spatial domain, in other words a receiver that may differentiate between signals depending on the direction of arrival. For GNSS, where interference and multipath (signal reflection off, for example, buildings or the ground) may be significant sources of error, this is an attractive solution. Although array processing have been the subject of extensive research efforts within other fields, there are several remaining issues with regards to how these techniques can be implemented in a GNSS receiver.With regards to array processing there are also properties unique to GNSS, such as multiple signal sources at known positions, that have not been explored sufficiently in previous efforts. In this thesis we show how these properties can be exploited to improve receiver performance in dynamic scenarios. In short, the orientation of the antenna platform is estimated accurately (typical variance around 1°) using beamforming techniques. This information is then used to achieve a better estimate of the radio environment by allowing for longer integration periods when estimating the covariance matrices. A better estimate of the covariance matrices directly translates into improved receiver performance, especially so in areas of moderate levels of multipath/interference.Further, a method to calibrate GNSS array antennas using real signals is investigated in detail. Instead of resorting to electromagnetic simulations that requires precise knowledge about the antenna and installation factors, or RF chamber measurement that is expensive, it is shown how the array antenna can be calibrated using live signals. The accuracy of the resulting model is verified using real data.Also, the first implementation of an RF record and replay system is presented. With such a system data can be recorded in a specific environment, generally a time consuming task, and later played back into the antenna input of any GNSS receiver. Such systems are nowadays commercially available and have proven very useful for testing and validation of GNSS receivers. Throughout the thesis, the required receiver architecture and practical viability of the proposed algorithms are considered.

  • 47.
    Backén, Staffan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Towards dynamic array processing for GNSS software receivers2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Since the very first Global Positioning System satellite was launched in 1978, Global Navigation Satellite Systems (GNSS) have developed into a world wide utility, providing everyone with an affordable method for determining accurate position and time. However, the system is susceptible to multipath (when the signal is reflected off a surface), interference (other signals in the same frequency band) and attenuation (for example canopies blocking some of the signal energy). Array processing of GNSS signals have lately drawn quite a bit of attention from the research community, where issues (susceptibility to interference, multipath and attenuation) can be mitiged to some degree. GNSS baseband processing is generally implemented in hardware (digital logic), although software based processing are swiftly gaining popularity among researchers. This thesis discusses the implementation of a software based GNSS array processing system with an emphasis on hardware, calibration and initial signal detection. Low cost, ASIC based front-ends are examined with regards to phase and gain stability, and are found to meet the requirements for array processing of GNSS signals. An antenna calibration technique using live GNSS signals (as opposed to anechoic chamber measurements) is proposed, where the predictable orbits and geometric diversity of GNSS are exploited. A system capable of replaying recorded narrow band GNSS signals into any low cost receiver is also discussed. Finally, efficient methods to acquire GNSS signals using an antenna array system are proposed.

  • 48.
    Backén, Staffan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Akos, Dennis
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Antenna array calibration using live GNSS signals2006Inngår i: Proceedings of the third ESA Workshop on Satellite Navigation User Equipment Technologies: NAVITEC 2006, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An anechoic chamber free approach to GNSS antenna array gain and phase calibration is proposed and evaluated for a stationary array. The constellation change of the satellites was used to measure the variations in gain and phase over two twelve hour periods. The results was compared to an array calibrated using traditional methods in an anechoic chamber. It is shown that the method agrees well with the traditional method. Care was taken to make sure interference and multipath levels were low.The processing is performed using acquisition and tracking loop software implemented in Matlab. The IF data is recorded with a multi front end recording system.

  • 49.
    Backén, Staffan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Akos, Dennis
    GNSS antenna arrays: hardware requirements for algorithm implementation2006Konferansepaper (Fagfellevurdert)
  • 50.
    Backén, Staffan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Akos, Dennis
    GNSS antenna arrays: hardware requirements for algorithm implementation2006Rapport (Annet vitenskapelig)
    Abstract [en]

    GNSS antenna arrays and beam forming/nulling have long been studied from an algorithm perspective. However, the hardware and implementation design issues are not as well understood. A low cost data collection platform for continuous recording of eight simultaneous IF streams are presented with an analysis of its performance. Also, the requirements on front end components are examined, specifically their impact on array processing versus single antenna processing. Focus is exclusively on digital beam forming as that is the only feasible approach for advanced algorithm implementation, and differences between traditional receiver architectures and a software defined radio approach will be emphasized. It is found that simultaneous recording of multiple IF streams allows for great flexibility in the field of antenna array processing for GNSS. Also, commercial off the shelf components shows sufficient performance, although care must be taken regarding issues such as phase consistency and cross talk between front ends.

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