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  • 1.
    Rune, Joel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013). Karlstads Universitet.
    Performance Estimation of a 1D pulsed LiDAR: A Study of SiPM-Based LiDAR in Ambient Light2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    LiDAR is a remote sensing technology that uses a laser to map the surrounding environment. With its many applications, for example in autonomous vehicles, LiDAR is a growing field within technology and research. The silicon photomultiplier (SiPM) is a solid state device commonly used in the receiving system of a LiDAR. However, ambient light from sun or other light sources is also seen by the photodetector which creates noise in the receiving system. The purpose of this work is to examine how the performance of a 1D LiDAR with a SiPM receiver can be predicted, given a certain level of ambient light, target reflectance and measuring distance. This was carried through by working with mathematical models and comparing the outcomes to lab measurements of a certain LiDAR model. The outcome showed that describing the performance of the particular LiDAR by a model based on incident photon rate was difficult mainly due to the unknown relation between how the voltage signal threshold in the receiving electric circuit for when the LiDAR stops the time measurement relates to the number of microcells activated in the SiPM during a time span. However, the results obtained suggest a threshold value of between around 20 and 60 microcells activated within a 1 ns time interval, but further tests are needed in order to confirm or reject this. Of the two other approaches tried, the signal voltage model gave reasonable results for the values tested but in a rather indirect way. The other approach, describing the connection between DC noise and AC RMS noise in the receiving system gave results deviating between 40% and 320% from the lab results, i.e. not so good match.

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  • 2.
    Ekblom, Filip
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Z2-Gauge Theory with Matter: Dispersive behaviour of a dimer in a 1+1-dimensional lattice2023Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The intention with this thesis is to investigate a dimer in a spin chain. Inorder to do that, a model from Z2-gauge theory is taken as the theoretical motivation to construct a discrete lattice with Ising spin properties. A dimer is then allowed to exist indirectly in the empty space between sites. We choose to tackle the problem through a quantum mechanical approach in 1+1-dimensions, distancing ourselves from the original description in quantum field theory. The exposition begins by reviewing the spatial construction of the entire chain as well as its components, and ends with a discussion of time development where the main concern is dispersion in addition to reflection against a static charge.

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  • 3.
    Enarsson, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    An Evaluation of the Condition and long term Degradation of Photovoltaic Installations using PVcheck2022Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Software for simulating the expected power production of photovoltaic installations is an important tool for monitoring the system condition. The purpose of this paper is to investigate modeling parameters and long term condition of existing up-and-running installations by using the software PVcheck. An evaluation of the software will be made with the intent of providing feedback that can be used to improve its functions. Central results in this paper include the proof of concept that a degradation analysis of photovoltaic installations can be made using PVcheck as well as showing an unexplained seasonal periodicity in results when using the Ineichen/Perez clear sky model in Glava, Sweden.

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    An-Evaluation-of-the-Condition-and-long-term-Degradation-of-Photovoltaic-Installations-using-PVcheck-Ulf-Enarsson
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  • 4.
    Arvidsson, Saga
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    LBIC Measurements on Busbarless Crystalline Silicon Solar Cells2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The importance of further research in the field of solar cells is crucial for the transition to cleaner energy. The aim of this project is to design and manufacture a contact system that can measure busbarless solar cells with an LBIC-system. In this project mono-crystalline busbarless solar cells were utilized, busbarless solar cells only have small fingers that go vertically.

    When an incident photon hits the solar cell it can be absorbed by the bulk material, by the pn-junction an electrical field will set the electrons in motion so an electrical current can be harvested. LBIC, which stands for light beam induced current is a technique to spatially map the quantum efficiency of a solar cell, there is also an availability to make phasemeasurements. There are two different quantum efficiencies, External quantum efficiency (EQE) and Internal quantum efficiency (IQE). The phase measurement of the LBIC shows how much resistance exists between the point of current-generation and the contacts where the current is collected.

    A contact system with a comb-like figure of phosphor bronze was manufactured and mounted on to the LBIC-machine. Several measurements were executed on two solar cells. This new contact system can measure busbarless solar cells, with a good connection to almost all the fingers on the solar cell. The lack of contact with some fingers seemed to not affect the end result too much. It isn’t vital to have contact with all fingers to get a decent LBIC-mapping.

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  • 5.
    Sjökvist, Emil
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Landberg, Simon
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Raytracing i Kanalmodellsimuleringar med GPU:er2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Eftersom att dataanvändningen runt om i världen är något som hastigt ökar måste tekniken hänga med den ständigt höga efterfrågan på data. 5G är en ny teknik som utvecklas för fullt och redan finns på vissa ställen i världen. Innan man installer arantenner och implementerar 5G i samhället skulle det underlätta om man först på något sätt skulle kunna simulera hur signalerna kommer att röra sig och träffa mottagare beroende på var man sänder ifrån och på så sätt få en uppfattning om hur och var det vore optimalt att installera 5G­sändare. Målet för projektet är att ta fram metoder, mjukvara och miljöer för att kunna utföra denna simulering samt använda en raytracer för att på ett så verklighetstroget sätt som möjligt skapa virtuella radiovågor. För att uppnå detta utfördes mycket forskning kring vad för mjukvara som är optimalt att använda för projektets ändamål och en stor mängd analysering av kodsamt experimentation inuti OptiX för att få förståelse för hur strålar genereras, färdas och interagerar i scenerna. Slutligen lyckades framtagning av all programvara som behövs för att utveckla simuleringen samt kan strålar skickas och användas i scenen med viss funktionalitet. Dock behövs vidare utveckling på projektet för att visualisera strålarna på ett korrekt sätt samt implementera flera av de fysiska egenskaperna.

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  • 6.
    Ryberg, Arvid
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Thawing, Scaling and Tracking QUintessence in a Phase Space Perspective: and comparisons to the ΛCDM model2022Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to give an introduction to quintessence models as well ascomparing those models with the currently accepted ΛCDM model. We willconsider quintessence in a spatially flat and isotropic Universe and useregular dynamical systems on a bounded three dimensional phase spacewhere we perform numerical calculations. This enables a globalunderstanding of these models and makes it possible to give thoroughdescriptions of the dynamics. We will discuss the three different types ofquintessence: Thawing, Scaling and Tracking quintessence and comparethem with the ΛCDM model. This thesis is based on several scientific papersand contains new numerical calculations and associated analysis.

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  • 7.
    Clarito, Samuel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    The Scattering matrix: Properties and one-dimensional examples2022Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The scattering matrix is used to relate particle states before and after undergoing a scattering process. It is used in quantum mechanics, scattering theory and quantum field theory. When quantum theory got developed, the classical descriptions for scattering were no longer sufficient and other methods began to develop. One of them being the S-matrix. In this thesis we present assumptions made in order to define the S-matrix, as well as its different properties and some one-dimensional examples. The definition of the S-matrix relates to the probability amplitude for different outcomes in a scattering experiment and the elements of the matrix are called scattering amplitudes. The S-matrix is unitary and if the scattering potential V (x) is real, it is also time-reversal invariant. In one dimension it is showcased how particles can transmit through or reflect off of a potential as well as how the symmetry of the potential effects the S-matrix. Lastly we give some examples of the S-matrix in one dimension and we end with a brief outlook of how it is defined and applied in quantum field theory where special relativity is taken into account.

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  • 8.
    Kaarna, Amanda
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Tsirelson's Bound: Introduction and Examples2022Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Tsirelson's bound is the upper bound for a Bell inequality which is valid for all quantum mechanical systems. We discuss why Tsirelson's bound was developed by looking at some historical arguments in quantum physics, such as the Einstein-Podolsky-Rosen (EPR) paradox, an argument for the quantum mechanical description of physical reality being incomplete, and local hidden variables. We present the counterargument to those theories, Bell's inequality, which later expanded to include any inequality that a local system fulfills, but that an entangled quantum system can violate. We present the proof of two specific Bell inequalities: the Clauser-Horne-Shimony-Holt (CHSH) inequality and the I3322 inequality. Then the Tsirelson's bound for the CHSH inequality is proven with a simple system of two entangled spin-1/2 particles and with a general argument that is valid for all entangled systems. We give the upper quantum bound for the generalized CHSH inequality, which describes the situation that we have more than two measurement options, by using semidefinite programming. We prove the Tsirelson's bound for the I3322 inequality by using maximally entangled systems and semidefinite programming. Finally, we discuss the upper bounds that are obtained from these different methods.

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  • 9.
    Brunzell, Albin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Tätning av Små Mekaniska Komponenter: Framtagning av Beräkningsmetod för Läckage2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Tändare finns i applikationer där det krävs en snabb tillförsel av energi, exempelvis airbags, i granatereller i riktade sprängverkan. Tändarens uppgift är att starta en detonation eller deflagering i ettsekundärt sprängämne av större mängd som har en hög aktiveringsenergi, genom att applicera en litenaktiveringsenergi initierar tändsatsen inuti tändaren. Tändare är små, inte ofta större än en inre volympå en kubikcentimeter. Då tändare är en kritisk del i en tändkedja ställs höga krav på dem, eftersom närett tillfälle sker när tändaren ska fungera måste den fungera. Kraven som ställs på tändare ärnödvändiga att följa för att funktionen ska bibehållas under produktens bestämda livstid, omprimärexplosivämnet i tändaren förstörs på grund av att det inte skyddats från ytter miljöpåverkanordentligt blir vare sig kunden eller tillverkare nöjda. För att skydda primärsprängämnet frånomvärlden krävs det att en tändare är tillräckligt tät, hur tät och mot vad den ska vara tillräckligt tätmot beror på miljöns påfrestningar. Problemet med dagens tändare är att de inte är tillräckligt täta mot fukt eller vattenånga. Små tändare som innehåller små mängder känsligt primärsprängämne kan snabbt bli förstört av fukt. Genom att bestämma hur tät tändaren måste vara för att primärsprängämnet inte ska förstöras går det attmotverka problemet. Målet med rapporten är att undersöka teoretiskt med hjälp av matematisk modellering vad som är tillräckligt tätt. Tre koncept på tätning av tändare kommer framtas och med hjälp av matematisk modellering avgörs vilken eller vilka koncept på tätning som är tillräckligt tät. Koncepten ska vara billiga, enkla att applicera på befintliga produkter och följa de krav som sätts på en tändare. Det acceptabla läckaget för en tillräckligt tät tändare togs fram att vara 10−7cm3/s av luft. Teoretisktgår det att få tändarna täta på ett simpelt sätt, koncept 1 och koncept 2 är båda tillräckligt täta om vissakriterier uppfylls. Koncept 2 är tätare än koncept 1 men har en mer komplicerad design.

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  • 10.
    Potter, Alexander
    Karlstad University.
    Tape solution in photovoltaic mini modules: A study into how the optical and electrical properties are affected by a novel method of assembling photovoltaic modules2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The goal of this thesis is to, on behalf of JB Eco Tech, investigate a novel method of interconnecting photovoltaic (PV) modules. The principle is to stick the interconnecting strings on the cells with a transparent tape instead of soldering. As a part of the assembly process, the module is laminated under heat which makes the strings stick to the PV cell. The method is going to reduce one step in the production process, replacing the soldering procedure with the lamination of the strings onto the cells. Also, the replacement of lead and silver will spare costs and the environment.

    To analyse the effects of the novel method on the performance of the cell, the optical properties of the module were investigated by mathematical models and Light Beam Induced Current (LBIC). Also, the electrical properties were compared to the conventional method of soldering by analysing the I-V characteristics. The experiments were done on mini modules.

    Although the mini module displayed a reflectance of about 5.7 – 6.0% the contribution of the tape only accounted for a maximum of 0.5%. Since the tape only covers a fraction of the cell, this reflectance is negligible. Only 3 modules were successfully analysed, and the electrical properties of the novel method did not differ from the conventional method. To solidify the later a claim a more extensive rapport has to be made. The thesis opens up a new research area where improvements to the novel method can be done.

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  • 11.
    Nilsson, Frida
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013), Science, Mathematics and Engineering Education Research.
    Hole transport layers in organic solar cells: A study of work functions in nanofilms2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Organic solar cells have been showing promise as a way of producing renewableenergy with the help of light, flexible, and production effective materials.The efficiencies and lifetimes reached in organic solar cells have steadily beenincreasing over the years as more research in the field is being conducted.One way of increasing the efficiency in organic solar cell devices is introducingan interlayer between the photoactive material and the anode, referred toas the ’hole transport layer’. Most commonly used as a hole transport layer isthe material PEDOT:PSS, which offers desired properties such as transparency,simple processing and good ohmic contact between anode and photoactive material.PEDOT:PSS is also known to be a degradation site in organic solar cells,as it will corrode the electrode in the presence of water.This project has consisted of investigating PEDOT:PSS along with two othercandidates that may one day come to replace PEDOT:PSS as the most commonlyused material, molybdenum trioxide (MoO3) and phosphomolybdic acid(PMA). The aim was to investigate how the different materials energy bandstructure would be affected upon exposure to sunlight, air and annealing, byobserving the work function under different conditions.

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  • 12.
    Rebecka, Vahlström
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies.
    Förskollärares kompetensutveckling och förutsättningar för undervisning av fysik i förskolan: En studie av sju förskollärares uppfattningar om deras kompetensutveckling och fortbildning i fysik samt förutsättningar för fysikundervisning i förskolan.2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to investigate seven in-service preschool teachers’ conception of their competence in physics, needs in further educational training and their perceptions around conditions surrounding physics education in preschool. The study is based on a phenomenographic approach where individual interviews have been conducted.The study shows that most of the preschool teachers feels that physics is difficult and something they are struggling with, both when it comes to teaching and understanding the subject themselves. Everyone in the study does not share these thoughts. The conception that also appears is that they do have good knowledge in the subject but not in teaching it. Most of the teachers are open minded in their needs of professional development. They express that they want education in the form of workshops, that both has a basic theoretical and practical approach. A minority feels that they can seek further development themselves through various types of literature. The study shows that there are many aspects of underlying conditions for why they do not teach preschoolers in physics. Perception that stands out are time-economic circumstances, their lack of knowledge in physics, lack of interest in the subject and arguments that indicate that they also use the preschoolers’ lack of interest as a defending argument.

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    Fulltext Rebecka Vahlström
  • 13.
    Berg, Henrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Radiation exposure to personnel during CT procedures2018Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    During X-ray examinations a large part of the radiation is scattered from the patient, contributing to larger radiation doses to medical staff operating inside the examination room. Ionizing radiation contributes to the risk of developing cancer and hereditary diseases but also to the risk of developing cataract.

     

    The aim of this thesis was to investigate the radiation environment and construct three-dimensional maps of the dose distribution, in a Computed Tomography (CT) room during examinations. 

     

    Air kerma was measured with real time dosimeters while irradiating an anthropomorphic phantom, using the X-ray tube voltages 100, 120 and 140 kV. The effective dose received by protected and unprotected medical staff inside the CT room during radiation exposure was estimated by using spectra from scattered X-ray radiation, a simulation of X-ray spectra and the dose evaluation program PCXMC. The equivalent dose to the eye lens was estimated by using spectra from scattered X-ray radiation and tabulated conversion factors from air kerma to the personal dose equivalent at 0.07 mm depth, Hp(0.07). From the estimated values of the effective dose and equivalent eye lens dose received by medical staff inside the room, three-dimensional dose distribution maps were constructed. The shielding effectiveness of a lead apron regularly used in the room was examined using tube voltages of 100, 120 and 140 kV.

     

    The radiation dose distributions have a maximum closest to the irradiated phantom for most heights except at eye level where the maximum is shifted outwards along the patient table due to strong shielding by the gantry at eye level. The strong shielding of the gantry is noticed for all energy levels and at all heights but is exceptionally noticeable at eye level. The shielding of the patient table is strongest for the lower heights but is also noticeable at eye level which may seem surprising since there were no objects between the phantom and that point. The dose distribution along directions with minimal shielding seems to follow the inverse square law well. The lead apron is effective but its efficiency decreases for higher photon energies which is expected.

     

    From information about the frequency and durations of CT-guided procedures, the estimated annual effective dose is 1.6-2.3 mSv for protected and 14.3-19.8 mSv for unprotected personnel at the operator position. The estimated annual equivalent eye lens dose is 4.7-7.8 mSv at the operator position. All annual doses at the operator position are below the annual threshold values of 20 mSv set by the ICRP.

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  • 14.
    Eriksson, Olof
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Radiation exposure to personnel during fluoroscopic procedures: Strålningsmiljö för personal under genomlysningsarbete2018Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    There are about 17 million X-ray procedures performed in Sweden every year. Various methods are used to determine the risk for the patient, and for the staff. The objective of this project was to map X-ray scatter coming out of a patient as a result of interactions between the radiation and body tissue during certain medical procedures that involve fluoroscopy. Flouroscopy is a type of X-ray imaging method that generates a moving picture which allows an operator to view in-body procedures live. A successfully created map of the radiation field can work as a tool for risk analysis concerning the dose of radiation of which the medical staff is exposed to, this parameter will later be described as the effective dose (E). The effective dose is a tool for assessment of the risk of developing lethal cancer due to radiation exposure. This report will also investigate the radiation that reaches the eye lens of the staff, since the maximum recommended dosage for the eye lens has been lowered recently when it was discovered that the eye lens was more sensitive to radiation than previously known. In this report data was collected from radiation exposure situations, and it was concluded that distance is a good protector against radiation, which agree well with theory discussed in the report. Another theory which was discussed in the paper states that positions behind the X-ray tube will be exposed to the highest amount of radiation, this was also proven. The measured data from investigating protective equipment showed that the equipment in place was effective.

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  • 15.
    Klippmark, Ellinor
    Karlstad University.
    Ytinitierat utmattningsbrott vid mycket höga cykler: Utmattningsprovning med ultraljudsutrustning följt av karaktärisering av brottytor i ett svepelektronmikroskop av ett höghållfast stål2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta projekt analyseras utmattningsbrott orsakade av ytdefekter i höghållfast stål som utsätts för fler än tio miljoner cykliska belastningar. Vanligen orsakas utmattningsbrott i denna region av interna materialdefekter där brottytan ofta innehåller ett område med grövre morfologi - fine granular area (FGA). FGA är en ackumulerad skada som bildas under sprickinitieringsstadiet och utgör cirka 99 % av den totala utmattningslivslängden. Resterande 1 % utgörs av spricktillväxt. På grund av detta är mekanismen som initierar sprickor i detta skede essentiell. Om FGA kan observeras vid ytinitierade utmattningsbrott för material som utsätts för fler än tio miljoner cykliska belastningar, är ännu inte fastställt. . Det här projektet syftar till att undersöka om FGA kan observeras i ytinitierat utmattningsbrott gällande material med väldigt långa livslängder, samt till att utreda hur ytinitieringar påverkar utmattningslivslängden. För att söka svar på dessa frågor utförs utmattningsprovning med ultraljudsutrustning, följt av karaktärisering av brottytorna i svepelektronmikroskop för att studera de morfologiska förändringarna. Vidare utförs finita element analyser med mjukvaran ABAQUS för att jämföra den maximala huvudspänningen mellan prov med, respektive utan ytdefekter. Resultatet från ABAQUS visar att proven med hårdhetsintryck utsätts för en större maximal huvudspänning än proven utan hårdhetsintryck, därigenom kan skillnaden i livslängder förklaras. . Testresultaten från utmattningsprovningen presenteras i ett S-N diagram som visar spänningsamplituden i förhållande till materialets livslängd. De analyserade bilderna från svepelektronmikroskopet av ytinitierat utmattningsbrott visar en antydan till FGA i två av 20 prov. Däremot tycks sprickorna, i samtliga fall, initiera på grund av ackumulering av plastisk deformation i ytan. Interna materialdefekter orsakade inte utmattningsbrott i något av de 20 testade proverna med ytdefekter. Två prover utan ytdefekter genomgick samma process och för båda dessa introducerades en spricka på grund av interna materialdefekter, båda innehöll ett tydligt FGA. Sammanfattningsvis indikerar resultaten från denna studie att FGA inte är lika uppenbara och eventuellt lika vanligt förekommande vid ytinitierat utmattningsbrott av höghållfasta stål med mycket långa livslängder. Även att ytdefekter introducerar en högre maximal huvudspänning i provets centrum, vilket resulterar i en kortare utmattningslivslängd. 

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    Ytinitierat utmattningsbrott vid mycket höga cykler
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  • 16.
    Karlsson, Eilind
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Kitaev models for topologically ordered phases of matter2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Condensed matter physics is the study of the macroscopic and microscopic properties of condensed phases of matter. For quite some time, Landau’s symmetry breaking theory was believed to describe and explain the nature of any phase transition. However, since the late 1980s, it has become apparent that it is necessary to introduce some new kind of order, named topological order, that transcends the traditional symmetry description. In this thesis we will study the Kitaev model, which is a Hamiltonian lattice model that allows one to incorporate the concept of topological order, as well as the corresponding operators and algebras. First, we consider the model on an infinite lattice, and show how to relate local and global degrees of freedom of the anyons/quasi-particles living on sites to the ribbon operators. Afterwards, we introduce holes and an external boundary to the lattice, and examine the ramifications of this generalization in terms of the ground state degeneracy. Lastly, we verify that the algebra formed by boundary site operators has the structure of a quasi-Hopf algebra. 

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  • 17.
    Ekhagen, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Silicon solar cells: basics of simulation and modelling: Using the mathematical program Maple to simulate and model a silicon solar cell2017Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The main goal of this thesis was to simulate a solar cell with the symbolic manipulation tool Maple and discuss the strength and weaknesses of using Maple instead of the already known simulation program PC1D. This was done mainly by solving the three essential differential equations governing the current density and excess electron and hole densities in the solar cell. This could be done easily by using known simplifications especially the low injection assumption. However it was also a success without using this particular simplification but the solutions had to be achieved using a numerical method instead of direct methods. The results were confirmed by setting up the same solar cell with PC1D. The conclusion is that Maple gives the user increased freedom when setting up the solar cell, however PC1D is easier to use if this freedom is not needed. At the end of this thesis a brief introduction is also made on the possibility of using Maple with a tandem cell setup instead of single junction.

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  • 18.
    Wilhelm, Söderkvist Vermelin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    3+1 Approach to Cosmological Perturbations: Deriving the First Order Scalar Perturbations of the Einstein Field Equations2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Experimental data suggest that the universe is homogeneous and isotropic on sufficiently large scales. An exact solution of the Einstein field equations exists for a homogeneous and isotropic universe, also known as a Friedmann-Lemaître-Robertson-Walker (FLRW) universe. However, this model is only a first approximation since we know that, locally, the universe has anisotropic and inhomogeneous structures such as galaxies and clusters of galaxies. In order to successfully introduce inhomogeneities and anisotropies to the model one uses perturbative methods. In cosmological perturbations the FLRW universe is considered the zeroth order term in a perturbation expansion and perturbation theory is used to derive higher order terms which one tries to match with observations. In this thesis I present a review of the main concepts of general relativity, discuss the 3+1 formalism which gives us the Einstein field equations in a useful form for the perturbative analysis, and lastly, I derive the first order scalar perturbations of the Einstein field equations.

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    3+1 Approach to Cosmological Perturbations
  • 19.
    Tyborowski, Tobias
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Determining the interwall spacing in carbon nanotubes by using transmission electron microscopy2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The interwall spacing of multi-walled carbon nanotubes has an effect on their physical and chemical properties. Tubes with larger interwall spacing - compared to the spacing where the carbon atoms are in their natural distance to each other - are for instance expected to be mechanically less stable. Considering the MWCNT interwall spacing’s dependence on the tube size, three interesting previous studies with slightly different conclusions can be found. All of them conclude an increase of the interwall spacing with a decreasing tube size. We describe their analysis procedure, compare them to each other and to our own measured data. In the beginning of our analyses, we determine the expected inaccuracy for measured distances out of TEM images being up to 10 % and we show the impacts of the TEM’s defocus, a powerful setting in TEM imaging. Finally, we suppose that the interwall spacings are not as strongly varying as one previous study concludes, but our analyses are relatively in harmony with the two other studies. The interwall spacings from tubes with an inner diameter larger than 5 nm are relatively constant within the whole tube. Furthermore, it appears that the middle spacings (excluding the outer- and innermost ones) show values that are most consistent with the interlayer spacings of turbostratic graphite. In underfocused images, the outer- and innermost spacings tend to have values being slightly smaller than the middle ones from the same tube. 

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  • 20.
    Svensson, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Path Integral for the Hydrogen Atom: Solutions in two and three dimensions2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The path integral formulation of quantum mechanics generalizes the action principle of classical mechanics. The Feynman path integral is, roughly speaking, a sum over all possible paths that a particle can take between fixed endpoints, where each path contributes to the sum by a phase factor involving the action for the path. The resulting sum gives the probability amplitude of propagation between the two endpoints, a quantity called the propagator. Solutions of the Feynman path integral formula exist, however, only for a small number of simple systems, and modifications need to be made when dealing with more complicated systems involving singular potentials, including the Coulomb potential. We derive a generalized path integral formula, that can be used in these cases, for a quantity called the pseudo-propagator from which we obtain the fixed-energy amplitude, related to the propagator by a Fourier transform. The new path integral formula is then successfully solved for the Hydrogen atom in two and three dimensions, and we obtain integral representations for the fixed-energy amplitude.

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  • 21.
    Edvardsson, Elisabet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Quasicrystals: Classification, diffraction and surface studies2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Quasicrystal is the term used for a solid that possesses an essentially discrete diffraction pattern without having translational symmetry. Compared to periodic crystals, this difference in structure gives quasicrystals new properties that make them interesting to study -- both from a mathematical and from a physical point of view. In this thesis we review a mathematical description of quasicrystals that aims at generalizing the well-established theory of periodic crystals. We see how this theory can be connected to the cohomology of groups and how we can use this connection to classify quasicrystals. We also review an experimental method, NIXSW (Normal Incidence X-ray Standing Waves), that is ordinarily used for surface structure determination of periodic crystals, and show how it can be used in the study of quasicrystal surfaces. Finally, we define the reduced lattice and show a way to plot lattices in MATLAB. We see that there is a connection between the diffraction pattern and the reduced lattice and we suggest a way to describe this connection.

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  • 22.
    Östersjö, Victor
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Supersymmetry for the Hydrogen Atom2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis it will be shown that the hydrogen atom has a SU(2) × SU(2) symmetry generated by the quantum mechanical angular momentum and Runge-Lenz vector operators. Additionally, the hydrogenic atom will be studied with supersymmetric methods to identify a supersymmetry that relates different such systems. This thesis is intended to present the material in a manner accessible to people without background in Lie groups and supersymmetry, as well as fill in some calculations between steps that are not spelt out in the litterature.

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  • 23.
    Sköld, Jennie
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ordering of Entangled States for Different Entanglement Measures2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Quantum entanglement is a phenomenon which has shown great potential use in modern technical implementations, but there is still much development needed in the field. One major problem is how to measure the amount of entanglement present in a given entangled state. There are numerous different entanglement measures suggested, all satisfying some conditions being of either operational, or more abstract, mathematical nature. However, in contradiction to what one might expect, the measures show discrepancies in the ordering of entangled states. Concretely this means that with respect to one measure, a state can be more entangled than another state, but the ordering may be opposite for the same states using another measure. In this thesis we take a closer look at some of the most commonly occurring entanglement measures, and find examples of states showing inequivalent entanglement ordering for the different measures.

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  • 24.
    Tang, Wai Ho
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Quantum Entanglement and Superconducting Qubits2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Conventional computing based on classical technologies is approaching its limits. Therefore scientists are starting to consider the applications of quantum mechanics as a means for constructing more powerful computers. After proposing theoretical methods, many experimental setups have been designed to achieve quantum computing in reality. This thesis gives some background information on the subject of quantum computing. We first review the concept of quantum entanglement, which plays a key role in quantum computing, and then we discuss the physics of the SQUIDs-cavity method proposed by Yang et al., and give the definitions of quantum gates which are the elements that are needed to construct quantum circuits. Finally we give an overview of recent developments of SQUIDs-cavity systems and quantum circuits after Yang et al.'s proposal in 2003. These new developments help to take a step towards the constructions of higher levels of quantum technologies, e.g. quantum algorithms and quantum circuits.

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  • 25.
    Andersson, Jonatan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    A lattice model for topological phases2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Matter exists in many different phases, for example in solid state or in liquid phase. There are also phases in which the ordering of atoms is the same, but which differ in some other respect, for example ferromagnetic and paramagnetic states. According to Landau's symmetry breaking theory every phase transition is connected to a symmetry breaking process. A solid material has discrete translational symmetry, while liquid phase has continuous translational symmetry. But it has turned out that there also exist phase transitions that can occur without a symmetry breaking. This phenomenon is called topological order. In this thesis we consider one example of a theoretical model constructed on a two dimensional lattice in which one obtains topological order.

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  • 26.
    Källstrand, Björn
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Optimal, universal quantum cloning2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The no-cloning theorem is one of the fundamental concepts of quantum information theory. It tells us that no general quantum state can be perfectly replicated. In this thesis we introduce the notion of imperfect cloning, and define the properties of the universal cloning machine. Furthermore, we construct an ansatz of how our universal cloning machine should perform as to produce two imperfect clones from one input qubit. We find an optimal fidelity of 5/6 for our universal cloning machine. We then reevaluate our ansatz and construct a class of unitary transformations such that an optimal fidelity is always achieved. Lastly, we present an overview of some applications of imperfect quantum cloning in the field of quantum information.

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  • 27.
    Thorén, Alexander
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Quantum teleportation and its experimental realization: Teleporting moving quantum states onto a stationary medium2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A quantum mechanical state may be transferred between locations using quantum teleportation.Specically information encoded in the polarized state of a light pulse maybe teleported onto the collective spin state of an ensemble of atoms. This thesis providesa theoretical framework for achieving such a teleportation protocol experimentally.

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  • 28.
    Al-Jaff, Mohammed
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    The ZX-Calculus: A graphical calculus for multipartite qubit systems2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis we will give a presentation of a graphical/diagrammatic calculus for quantum systems involving interacting quantum observables such as multi-partite systems of qubits, the ZX-Calculus. Unlike the Hilbert space formulation of quantum mechanics, the ZX-Calculus is based on category theory, more specically on the notion of a compact dagger symmetric monoidal category and as a consequence the graphical language associated with such a category is inherited by the calculus. This enables us to think about and deal with many calculations in quantum computation and information in a purely graphical and intuitive fashion. Although being formulated in a more general mathematical framework, huge parts of the Hilbert space formulation of quantum mechanics can be extracted from the ZX-calculus. In this thesis we will begin by giving a motivation for the need of such a calculus and then key concepts of category theory will be introduced in an intuitive manner in order to understand the ZX-calculus that will be presented afterwards. We then apply the calculus to'model' and describe certain quantum circuits and quantum teleportation.

  • 29.
    Flygare, Mattias
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Holonomic versus nonholonomic constraints2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Courses in analytical mechanics for undergraduate students are often limited to treatment of holonomic constraints, which are constraints on coordinates. The concept of nonholonomic constraints, constraints on velocities, is usually only mentioned briefly and it is easy to get a wrongful idea of what they are and how to treat them. This text explains and compares the methods of deriving the Euler-Lagrange equations and the consequences when imposing different kinds of constraints. One way to properly treat both holonomic and nonholonomic constraints is given, pinpointing the difficulties and common errors. Along the way, the treatment in local coordinates is also put in more modern terms, in the language of differential geometry, which is the language most commonly used in modern texts on the subject.

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    Flygare_Studentuppsats
  • 30.
    Juteräng, David
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Polymera solceller på färgtäckt tunnplåt: En genomförbarhetsstudie2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den här uppsatsen handlar om att undersöka om polymera solceller kan tillverkas på stålsubstrat. Polymera solceller är ett alternativ till kristallina solceller och tunnfilmssolceller där organiska material med halvledaregenskaper, det vill säga konjugerade molekyler och polymerer, används för att tillverka det aktiva lagret i solceller. Ett framgångsrikt sätt att tillverka sådana solceller är att blanda givarmolekyler och mottagarmolekyler i det aktiva skiktet. Detta kallas för en bulk-heteroövergång. När ljuset faller på skiktet exciteras en elektron i givarmaterialet och överförs till mottagarmaterialet. Ett elektriskt fält transporterar ut elektronen till en kontakt. Det är detta som ger upphov till strömmen i en polymersolcell.

     

    Polymera solceller har tillverkats på substrat av färgtäckt stål. Stålsubstratens ytegenskaper undersöktes för olika beläggningar och några potentiella substrat selekterades. Eftersom dessa substrat är ogenomskinliga behöver toppkontakten vara transparat. Detta kan uppnås genom att applicera solcellens skikt i omvänd ordning mot vad som är brukligt för polymera solceller. Den här typen av uppbyggnad kallas för en inverterad struktur och är lämplig för solceller på stål. En inverterad struktur användes med silver som bottenkontakt och PEDOT:PSS som toppkontakt. Det aktiva skiktet utgjordes av en blandning av poly-hexyltiofen och en fullerenderivat. De färdigtillverkade solcellernas elektriska egenskaper uppmättes och tydliga diodegenskaper noterades. Dock uppvisade solcellerna ingen fotoström. De aktuella substraten bedömdes vara för grova för att användas vid tillverkning av polymera solceller. Framtida studier bör inrikta sig på släta metallsubstrat istället. Alternativa tillvägagångssätt och förbättringar diskuteras.

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    Solceller på tunnplåt
  • 31.
    Strömwall, Joakim
    Karlstad University, Faculty of Technology and Science.
    Staggered Ladder Spectra2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
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  • 32.
    Isaksson, Mikael
    Karlstad University, Faculty of Technology and Science.
    Aspects of spatially homogeneous and isotropic cosmology2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, after a general introduction, we first review some differential geometry to provide the mathematical background needed to derive the key equations in cosmology. Then we consider the Robertson-Walker geometry and its relationship to cosmography, i.e., how one makes measurements in cosmology. We finally connect the Robertson-Walker geometry to Einstein's field equation to obtain so-called cosmological Friedmann-Lemaître models. These models are subsequently studied by means of potential diagrams.

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    FULLTEXT01
  • 33.
    Andersson, Mattias
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Scalar fields on star graphs2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

     A star graph consists of a vertex to which a set of edges are connected. Such an object can be used to, among other things, model the electromagnetic properties of quantum wires. A scalar field theory is constructed on the star graph and its properties are investigated. It turns out that there exist Kirchoff's rules for the conserved charges in the system leading to restrictions of the possible type of boundary conditions at the vertex. Scale invariant boundary conditions are investigated in detail.

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  • 34.
    Yngman, Sofie
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Probing mechanical properties of carbon nanotubes2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose with this c-level thesis is to investigate Young’s modulus of carbon nanotubes (CNTs). The force measurements as well as the imaging are done by an atomic force microscope (AFM). This has been done before by Eric W. Wong et al in 19971. These earlier experiments report techniques using clean-room facilities not available at Karlstad University. Our task is to investigate probabilities in which to perform the experiment by using the available instruments at Karlstad University.The force measurements are done by using the AFM tip to push the CNTs. A force curve is obtained from where it is possible to determine the spring constant of the CNT. By knowing some essential characteristics of the cantilever and the tip, Young’s modulus can be calculated. The CNT needs to be fixed in one end and able to push to the sides in the other end. Our main focuses in this thesis is how to fix the CNTs and what surface to use. Essentially two methods of fixing the tubes have been tried out. Partly we have been looking for large particles on the surface lying on top of a CNT fixing one end, partly we have evaporated gold to achieve an edge under which the CNTs can be attached.In conclusion we can say that it is hard and time-consuming looking for CNTs randomly fixed by particles on the surface. Further we can say that the choice of surface is important. A surface with a low friction was desired but the low friction causes trouble during imaging. The force between the tip and the cantilever during imaging seems to be enough to disturb the CNT and the surface, making measurements hard.

  • 35.
    Hultgren, Kristoffer
    Karlstad University, Faculty of Technology and Science.
    Cosmological Density Perturbations2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    This thesis presents a brief review of gravitation and cosmology, and then gives an overview of the theory of cosmological perturbations; subsequently some applications are discussed, such as large-scale structure formation. Cosmological perturbations are here presented both in the Newtonian paradigm and in two di¤erent relativistic approaches. The relativistic approaches are (i) the metric approach, where small variations of the metric tensor are considered, and (ii) the covariant approach, which focusses on small variations of the curvature. Dealing with these two approaches also involves addressing the gauge problem –how to map an idealized world model into a more accurate world model.

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    FULLTEXT01
  • 36.
    Westrich, Quinton
    Karlstad University, Faculty of Technology and Science.
    Lie Algebras in Braided Monoidal Categories2006Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    We begin by recalling some basic definitions from Lie algebra theory to motivate our subsequent transition to the more general setting of category theory. Next, we develop a relatively self-contained introduction to those areas of category theory needed for an understanding of what follows. Here we also motivate and introduce the graphical calculus notations. We then state the definitions of a braided commutator algebra, a braided Lie algebra, and a braided commutator Lie algebra. We proceed to show that color Lie algebras and Lie superalgebras are examples of braided Lie algebras. Thus, we are interested in examining color Lie algebras and Lie superalgebras in the generalized setting of braided Lie algebras. So we end by examining the representation theory of braided Lie algebras and braided commutator Lie algebras. In paricular, we find analogues of the adjoint representation, the tensor product representation, and the contragredient representation.

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  • 37.
    Persson, Anna
    Karlstad University, Faculty of Technology and Science.
    MBL-laborationers effektivitet i gymnasieskolans fysikundervisning: -Modern teknik eller framgångsrik pedagogik?2006Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [sv]

    Den här uppsatsen är en didaktisk uppsats i fysik som beskriver ett projekt där syftet var att undersöka om det är den moderna tekniken eller pedagogiken som är orsaken till MBL-laborationers effektivitet. Förkortningen MBL står för Microcomputer Based Laboratory. Projektet genomfördes i en klass på naturvetenskapliga programmet vid en gymnasieskola i Arvika.

    Eleverna fick utföra en MBL – laboration som handlade om impuls och rörelsemängd. Halva gruppen fick utförliga instruktioner med stödfrågor enligt MBL-pedagogik och den andra gruppen fick en instruktion av formelverifikations typ och använde MBL – utrustningen endast som tekniskt hjälpmedel.

    Utvärderingen av projektet bestod av att eleverna fick besvara en enkät med frågor om rörelsemängd och impuls före och efter laborationen. Elevernas resultat på testfrågorna visade att den gruppen som fick MBL – pedagogik förbättrade sina resultat efter laborationen i större utsträckning än den gruppen som endast använde MBL-tekniken. Slutsats från projektet är att pedagogiken har stor betydelse för elevernas lärande.

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