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  • 1.
    Akeab, Imad
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Accurate techniques for 2D electromagnetic scattering2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of three parts. The first part is an introduction and referencessome recent work on 2D electromagnetic scattering problems at high frequencies. It alsopresents the basic integral equation types for impenetrable objects. A brief discussionof the standard elements of the method of moments is followed by summaries of thepapers.Paper I presents an accurate implementation of the method of moments for a perfectlyconducting cylinder. A scaling for the rapid variation of the solution improves accuracy.At high frequencies, the method of moments leads to a large dense system of equations.Sparsity in this system is obtained by modifying the integration path in the integralequation. The modified path reduces the accuracy in the deep shadow.In paper II, a hybrid method is used to handle the standing waves that are prominentin the shadow for the TE case. The shadow region is treated separately, in a hybridscheme based on a priori knowledge about the solution. An accurate method to combinesolutions in this hybrid scheme is presented.

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  • 2.
    Khodadad, Davood
    Luleå University of Technology.
    Combined Digital Holography and Speckle Correlation for Rapid Shape Evaluation2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing thecontrolled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. In digital holography, access to the complex wave field and the possibility tonumerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single exposure,which is important when doing measurements in a disturbed environment.The aim of this thesis is to perform online process control of free-form manufactured objects by measuring the shape and compare it to the CAD-model. To do this, a new technique to measure surface gradients and shape based on single-shot dual wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape and position without the unwrapping problems that usually appear in dual wavelength holography. The method is firstdemonstrated using continues wave laser light from two temperature controlled laser diodes operating at 640 nm. Further a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. One significant problem when using the dual wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows single-shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a single-shot dual wavelength calibration is reported by defining a criteria to make an automatic procedure.By the results of the presented work, it is experimentally verified that the single-shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. The proposed method is also robust to large phasegradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, the shape measurement can be done even though the synthetic wavelength is out of the dynamic range of the height variation of the object.

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  • 3.
    Dahlin, Michael
    Linnaeus University, Faculty of Arts and Humanities, Department of Cultural Sciences. Kalmar Läns Museum.
    I rösebyggares land: en studie av Misterhults bronsålder2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In this work, I have mainly aimed to show how the results of previous field surveysin Misterhult parish, Småland province, Sweden have influenced past andcurrent research. Targeted surveys may in fact still change the picture radically.Our state of knowledge may also change through reviews of previous fieldworkand new excavations targeted at knowledge gaps. I have discussed Misterhult’sBronze Age and problems in that field. I have emphasised our current state ofknowledge and made a call for further fieldwork in the area. There is still muchto be done, and this study pinpoints what, in order to approach an answer towhat attracted people to the area 3000 years ago. Misterhult is one of NorthernEurope’s most extensive and best preserved Bronze Age settled landscapes, andconditions for research are good.In addition to surveys and the spatial site distribution, my focus has been on theunderlying economy, i.e. the economy behind the burial-cairn environments. Ihave tried to show that the economy was crucial to the design and ritualisationof those environments.

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  • 4.
    Tresch, Nathalie
    University of Gothenburg, Sweden.
    Le Dévoilement d’autrui dans les oeuvres littéraires: Aspects littéraires et juridiques2014Licentiate thesis, monograph (Other academic)
    Abstract [sv]

    I Frankrike, men även i andra länder, har under senare tid problematiken med litterära verk som skildrar privata förhållanden, till synes relaterade till verkliga personer, allt oftare aktualiserats i såväl media som rättsprocesser. Föreliggande studie syftar till att analysera vad som sker då en person, som anser sig ha fått privatlivets helgd kränkt i ett litterärt verk, drar författare och förlag inför domstol. Problematiken involverar konfrontationen mellan två grundläggande rättigheter: å ena sidan varje författares rätt att uttrycka sig fritt, å den andra den enskilda individens rätt att värna sitt privatliv. Detta dilemma leder till frågan om hur långt en romanförfattare får lov att gå i sin framställning av förhållanden som tillhör existerande personers privata sfär. Licentiatuppsatsen diskuterar olika definitioner av begreppet privatliv i förhållande till i Frankrike gällande lagstiftning. Vidare undersöks i vilken utsträckning domare behandlar till exempel faktatexter och fiktionstexter olika. Analysen visar att rättspraxis varierar från en domstol till en annan, liksom att domarna ofta hänvisar till de aktuella texternas litterära genretillhörighet, vilken i praktiken kan vara svår att fastställa. De texter som används som exempel i uppsatsen har av sina förläggare lanserats som romaner, samtidigt som de alla i någon utsträckning blandar fiktion med fakta. Detta har i flera fall lett till att domstolarna omdefinierat verken genremässigt, ett förfarande som också fått konsekvenser för utslaget. En intressant fråga i sammanhanget är huruvida domstolarna är kompetenta att göra denna bedömning och vilka kriterier de baserar den på. Uppsatsen är tänkt att utgöra första delen av en doktorsavhandling, där dessa frågor kommer att undersökas vidare, bland annat i avsikt att utröna möjligheterna till förbättringar och tydliggöranden inom aktuell lagstiftning.

  • 5.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local variation in bending stiffness in structural timber of Norway spruce: for the purpose of strength grading2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most strength grading machines on the European market use an averagemodulus of elasticity (MOE), estimated on a relatively large distance along awood member, as the indicating property (IP) to bending strength. Theaccuracy of such grading machines in terms of coefficient of determination israther low at R2 ≈ 0.5. This research is motivated by a desire to increase theaccuracy of the strength grading in the industry today. The aim of the presentstudy is to contribute knowledge of local variation in bending stiffness/MOEwith high resolution and thus locate weak sections due to stiffness reducingfeatures (the most important is knots) for structural timber.The present study introduces three methods that involve structural dynamics,classical beam theory and optical measurement to assess local wood stiffness.Specifically:

    • The dynamic method, in which a wood member is treated as an ordinaryphysical structure and the local stiffness is studied by exploring itsdynamic properties.
    • In Method II, a bending MOE profile is established based on local fibre angle information. The local fibre orientation is detected through highresolution laser scanning based on the tracheid effect.
    •  For Method III, a bending MOE profile is established using surfacestrain information under four-point bending. A high resolution strainfield is obtained using the digital image correlation (DIC) technique.

    From the present study, the two latter methods are more favourable inevaluating the local stiffness within a piece of structural timber. Moreover, thestudy reveals that the established bending MOE profiles using the two lattermethods, i.e. based on information of the local fibre angle and surface strain,agree reasonably well. However, for some patterns of knot clusters, the localbending MOE, calculated on the basis of fibre angles, is significantly higherthan the local bending MOE estimated on the basis of surface strain.

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    Licentiate thesis
  • 6.
    Chen, Yousheng
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Model Calibration of Nonlinear Mechanical Systems Using Multi-Harmonic Frequency Response Functions2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In industry, linear finite element models are commonly employed to represent global structural behavior. It is crucial that the computational models are able to accurately represent the structures’ behavior. This cannot always be achieved by the use of linear models.

    When vibrational test data show significant nonlinear characteristics, an initial linear finite element model may be judged insufficient in representing the structural behavior. Although an initial model can give a good foundation for the understanding of the dynamic behavior of the structure, the parameters that capture the nonlinear effects are most likely not included. Therefore, a set of candidate parameters controlling the nonlinear effect have to be added. The selection of such candidates is a delicate task which solution is preferably supported by engineering insight into the characteristics of the structure.

    One part of this work is on the selection of parameters, among all possibly uncertain properties, together with the forming of the objective function to be used for calibration. To obtain precise estimates of the parameters, the objective function data have to be informative with respect to the selected parameters. Further the parameters have to be identifiable. To improve these qualities, a multi-harmonic sinusoidal excitation was designed since the corresponding steady-state responses at the sub- and super- harmonics were shown to contain valuable information for the calibration process. Model calibration of nonlinear systems made by minimizing the differences between predicted and measured multi-harmonic frequency response functions.

    Further, in the calibration, multi-harmonic frequency response functions need to be calculated recurrently in order to reach convergence; therefore a fast simulation scheme was required. The performance of computations of multi-harmonic frequency response functions calculated using time domain as well as frequency domain simulation techniques were studied and compared.

    Finally, the proposed calibration method was validated by use of experimental testing on a replica of the Ecole de Lyon nonlinear benchmark structure. It was shown in the validation results that the predictions stemming from the calibrated model matched the experimental data well.

  • 7.
    Dai, Deliang
    Linnaeus University, School of Business and Economics, Department of Economics and Statistics.
    Moments, factor scores and limiting distributions of individual Mahalanobis distances2014Licentiate thesis, comprehensive summary (Other academic)
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  • 8.
    Markkanen, Peter
    Linnaeus University, Faculty of Technology, Department of Mathematics, Department of Mathematics Education.
    "Tekniken utan en lärare är ingenting": En studie om användande av teknik i geometriundervisning2014Licentiate thesis, monograph (Other academic)
    Abstract [sv]

    Målet med denna avhandling är att bidra med kunskap om hur digital teknik kan bidra till att utveckla matematikundervisning. I studien riktades intresset mot undervisning i tredimensionell geometri som skedde med stöd av interaktiva skrivtavlor. Syftet varatt studera hur läraren utnyttjar tekniken för att skapa matematiska situationer vilka kan möjliggöra lärande. Studien har en etnografisk inriktning där forskaren under fem veckor följdeen lärares teknikunderstödda undervisning i en klass i årskurs 9. Det empiriska materialet samlades in genom videounderstödd observation, intervju med läraren, fokusgruppsintervjuer med elever samt elevtester. Detta materialanalyserades med fokus på desätt på vilka läraren utnyttjar tekniken för att lyfta fram och arbetamed det matematiska innehållet. Resultatet visar att läraren utnyttjar flertalet strategier som tekniken erbjuder för att representera det matematiska innehållet och med teknikens hjälp växla mellan olika representationsformer, t.ex. genom att bearbeta, flytta och klona geometriska figurer. Läraren är överlag positiv till användande av teknik i matematikundervisningen, och de fördelar med tekniken som hon lyfter fram är att den hjälper och understödjerhenne utifrån de behov som uppstår i undervisningen och ger henne fler verktyg att belysa sådant som en del elever kan ha svårt att få syn på. Resultatet visar även att det fordras mycket arbete av läraren att sätta sig in i teknikens möjligheter och anpassa dessa till den egna undervisningen. Även eleverna är positiva till undervisning som sker med stöd av teknik då de menar att det hjälper dem att skapa sig en förståelse för tredimensionell geometri. Detta stärks av resultaten på det uppföljandetest som genomfördes efter arbetsområdet vilket visar att eleverna på ett påtagligt sätt utvecklat sin förståelse för geometriska begrepp.

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  • 9.
    Bengtsson, Anna
    Linnaeus University, Faculty of Technology, Department of Mathematics, Department of Mathematics Education.
    When mathematics teachers focus discussions on slope: Swedish upper secondary teachers in a professional development initiative2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The shift towards collegiality is a new setting for many teachers. Most teachers work alone, in isolation from their colleagues and collegial collaboration requires organisational structures. The aim of the study is to describe and analyse upper secondary mathematics teachers’ collective practice,developed in a professional development initiative. This study is a case study and the empirical data is generated through observations and an interview of a group of four teachers at a school who met on a weekly basis throughout a term. Their discussions focused on the mathematical concept of slope in a setting of learning study. This thesis is the case of when mathematics teachers focus discussions on slope and draws on Wenger’s Communities of Practice Perspective, as a unitof analysis, and addresses the question: What are the characteristics of practice when upper secondary mathematics teachers focus discussions on slope in the setting of a learning study? The analysis accounts for characteristics of the aspects of practice, through the coherence of mutual engagement, joint enterprise and shared repertoire in the community of practice. The teachers are engaged around finding small changes in their teaching that could give major effect in students learning. They negotiate what the students need to know in order to understand the relation between Δy and Δx. The characteristic of practice is a conceptual mapping of the concept of slope. It reveals students’ partial understanding of related concepts due to how they were given meaning through previous teaching. The conceptual mapping of slope goes back as far as to the student’s partial understanding of the meaning of subtraction. However, what emerges is in relation to the teachers’ experience of avoiding students’ difficulties with negative difference when teaching slope. It turns out to be a negotiation and a renegotiation of teaching slope for instrumental understanding or conceptual understanding. An overall characteristic of practice is that it develops in a present teaching culture.

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