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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Interpolation and visualization of sparse GPR data / Interpolering och visualisering av gles GPR data

Sjödin, Rickard January 2020 (has links)
Ground Penetrating Radar is a tool for mapping the subsurface in a noninvasive way. The radar instrument transmits electromagnetic waves and records the resulting scattered field. Unfortunately, the data from a survey can be hard to interpret, and this holds extra true for non-experts in the field. The data are also usually in 2.5D, or pseudo 3D, meaning that the vast majority of the scanned volume is missing data. Interpolation algorithms can, however, approximate the missing data, and the result can be visualized in an application and in this way ease the interpretation. This report has focused on comparing different interpolation algorithms, with extra focus on behaviour when the data get sparse. The compared methods were: Linear, inverse distance weighting, ordinary kriging, thin plate splines and fk domain zone-pass POCS. They were all found to have some strengths and weaknesses in different aspects, although ordinary kriging was found to be the most accurate and created the least artefacts. Inverse distance weighting performed surprisingly well considering its simplicity and low computational cost. A web-based, easy-to-use visualization application was developed in order to view the results from the interpolations. Some of the tools implemented include time slice, crop of a 3D cube, and iso surface.
282

Properties of cluster-size heterogeneity near the phase transition in the two-dimensional Ising model

Kauppi, Renée January 2020 (has links)
Two different definitions of cluster-size heterogeneity are investigated as well as correlation time of different quantities using the Metropolis algorithm and the Wolff algorithm. It is confirmed that the correlation time multiplied by the computation time is lower for the Wolff algorithm in an area around the critical temperature. It is also confirmed that one definition of the heterogeneity has a local maximum at the critical temperature where as the other has an abrupt change in derivative. The local maximum appears with L ≥ 64 and it is predicted but not verified that systems with L > 43 have such a maximum. The relationship between the number of distinct cluster sizes for clusters with spin-up and spin-down is investigated and it is observed that these transition from being significantly different at lower temperatures to being mostly similar at higher temperatures. The point of transition appears to be near the critical temperature.
283

The Quantum Hall Effect

Grälls, Conrad January 2020 (has links)
The quantum Hall effect occurs when a conductor carrying a current is placed in a perpendicular magnetic field. If certain conditions are met, such as strong magnetic field and low temperature, the resistivity becomes quantised, taking values of integer or fractional multiples of h/e2. By analysing the movement of electrons in a magnetic field classically and quantum mechanically information about the integer quantum Hall effect and the fractional quantum Hall effect can be gathered, using the two different gauge potentials of Landau gauge and Symmetric gauge. Resistance Metrology is one field of study that the quantum Hall effect has greatly impacted by providing a way to universally maintain the ohm, with significantly less uncertainty than previously. / Den kvantmekaniska hall-effekten uppstår när en strömbärande ledare placeras i ett vinkelrätt magnetfält. Om vissa villkor är uppfyllda, såsom starkt magnetfält och låg temperatur, blir resistiviteten kvantiserad. Given av heltal (integer) eller fraktions-(fractional) multiplar av h/e2. Genom att analysera elektroners rörelse i ett magnetfält klassiskt och kvantmekaniskt fås information om Hall-effekterna; integer quantum Hall effect och fractional quantum Hall effect, med hjälp av de två gauge potentialerna Landau gauge och Symmetrisk gauge. Resistansmetrologi är ett forskningsområde som kvant Hall-effekten har starkt påverkat genom att tillhandahålla ett sätt att universellt upprätthålla ohm-enheten med betydligt mindre osäkerhet än tidigare.
284

En analys av hur en undervisning med Investigative Science Learning Environment (ISLE) bör påverka elevers syn på fysik, fysikinlärning och fysikexperiment. Samt en svensk översättning av två Research-Based Assessment Instruments (RBAIs) - CLASS och ECLASS. / An analysis of how instruction that uses the Investigative Science Learning Environment (ISLE) is expected to impact students’ attitudes and beliefs about physics, physics learning and physics experimentation; and Swedish translations of two Research-Based Assessment Instruments (RBAIs) – CLASS and ECLASS

Henriksson, Johan January 2020 (has links)
Först ges en beskrivning av undervsiningsfilosofin Investigative Science Learning Environment (ISLE) och research-based assessment instruments (RBAIerna) CLASS och ECLASS, följt av en översättning till svenska av RBAIerna. En analys skedde sedan av hur svaren till påståendena i RBAIerna (pre- vs post-) förväntas ändras om en ISLE-baserad undervisning ges. I analysen försökte jag koppla påståendena till någon eller några av de sex vetenskapliga förmågorna och deras tillhörande bedömningsmatriser, vilka nu är en integrerad komponent i ISLE filosofin, men som ursprungligen utvecklades av Rutgers Physics and Astronomy Education (PAER) group. Jag använde även litteratur om ISLE och textboken "College Physics: Explore and Apply", vilken används i ISLEbaserade kurser, för att analysera påståendena. Resultatet blev att en majoritet av alla påståenden - 72\% av CLASS- och 77\% av ECLASSpåståendena - bör besvaras mer expertlikt efter en ISLE-baserad undervisning än innan. Ett påstående i CLASS, vilket motsvarar 3\% av påståendena i enkäten bedömdes även besvaras mindre expertlikt och resterande kunde jag inte, utifrån min analysmetod förutsäga om de skulle besvaras mindre, lika eller mer expertlikt. Efter analysen och undersökningar av tidigare studier om studenters prestationer på CLASS- och ECLASSenkäterna, formulerades en förutsägelse att en ISLE-baserad undervisning bör leda till att elever svarar mer expertlikt än om de undervisas traditionellt. En pilotstudie av den svenska översättningen genomfördes sedan på elever inom olika utbildningsnivåer mellan gymnasie- och doktorandnivå. Resultatet analyserades och jämfördes med tidigare forskning i andra länder, även om både skillnader och likheter kunde hittas var det svårt att dra några generella slutsatser på grund av få svarande i min studie. / A description of the teaching philosophy Investigative Science Learning Environment (ISLE) and the research-based assessment instruments (RBAIs) CLASS and ECLASS are given, followed by a translation of the RBAIs into Swedish. An analysis is then made of how the answers to the RBAIs (pre- vs. post-) are expected to change if students take an ISLE-based physics course. In the analysis, I tried to connect the statements to one or more of the six scientific abilities and their associated rubrics, which are now a component of the ISLE philosophy but are originally developed by the Rutgers Physics and Astronomy Education (PAER) group. I did also use literature about ISLE and the textbook “College Physics: Explore and Apply” which is used in ISLE based courses, to analyze the statements. I found that that the majority of the statements - 72 \% in CLASS and 77 \% in ECLASS – are expected to be answered in a more expert-like way after an ISLE-based course. One statement in CLASS, which corresponds to 3 \% of the statements in the survey, is expected to be answered in a less expert-like way. For the rest of the statements I could not predict, using my method of analysis, if they would be answered less, equally or more expert-like.  After performing the analysis and examining the existing research literature on student performance on CLASS and ECLASS surveys, a prediction that ISLE-based teaching should lead to more expert-like answers than traditional teaching is formulated. Results from a recent empirical study done in the US, published after my analysis was complete, appear to be in agreement with the prediction that follows from my analysis. A pilot study of the Swedish translations of CLASS and ECLASS was also performed on students at different educational levels, ranging from upper secondary to doctoral level. The results were analyzed and compared to previous research in other countries. Although both differences and similarities could be found, it was not possible to draw any general conclusions due to the small number of respondents in my study.
285

Lärande för hållbar utveckling i tidig grundskola : En studie om erfarna lärares uppfattningar om hållbar utveckling och lärande för hållbar utveckling / Education for sustainable development in primary school : A study on experienced teachers' perceptions of sustainable development and education for sustainable development

ELIN, GUSTAVSSON January 2020 (has links)
Sustainable development and education for sustainable development are something that characterizes our society today. Every day we are fed from different media about the future of our world and that we should think sustainably in everything we do. In the curriculum of the compulsory school it is mentioned in several places that the school should work on sustainable development (Skolverket 2019). Today´s teachers have a greater responsibility to teach students to become democratic citizens who are thinking and acting for sustainable development. Students should think sustainably in everything they do. Everything from sharpening a pen just enough to not throwing away food.The purpose of the study was to illustrate the teachers' perceptions of learning for sustainable development and to see how it is implemented in teaching that is education for sustainable development. Based on the purpose of the study, a qualitative study was conducted. Seven teachers, from a school in a mid-Swedish town, that works expcitly with education for sustainable development.The results indicate the importance of cross-disciplinary work with a certain complexity, where professional development and teachers working teams are important parts of the teaching and learning strategy. It also appears that school cultivation and other practicalities are of great importance to education for sustainable development along with the students' impact on the environment in the classroom and their sustainability thinking in everything they do during the school day.
286

Electrochemical investigation of "green" film-forming corrosion inhibitors : / Elektrokemisk undersökning av "grön" filmbildande korrosionsinhibitorer :

Wang, Hansheng January 2011 (has links)
In this work, a comparative electrochemical study has been performed to evaluate corrosion inhibition property of several film-forming corrosion inhibitors provide by Akzo Nobel on carbon steel in a chloride solution. For carbon steel exposed to 1 M NaCl solution with and without added inhibitor, electrochemical measurements including electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) at different exposure time intervals, and potentiodynamic polarization at the termination of the exposure, have been performed to investigate the film forming process and to evaluate corrosion inhibition efficiency of the inhibitors, as well as its evolution with time. The corrosion resistance data obtained from the EIS and LPR measurements are in good agreement. The results indicate different inhibition properties of the inhibitors tested. The inhibition effect of SSF CI-1 is negligible in the first hour of exposure, but it increases steadily with time for 1 day, and then remains the same level during the exposure up to one week. SSF CI-2 exhibits a good inhibition effect in the first hour, but the effect decreases with time to a low level after 8 hours, and then increases again with prolonged exposure. SSF CI-4 shows a low inhibition effect during the first day, and then increases to a maximum level after three days’ exposure. For SSF CI-5 and SSF CI-6, the inhibition effect within 8 hours is relative low but higher than that of SSF CI-4, and the effect increases with time during prolonged exposure. The SSF CI-5 seems to be better than SSF CI-6 because of a more stable inhibition effect. The EIS results indicate that most of the inhibitors form a resistive surface film on carbon steel, which becomes more resistive and protective after several days’ of exposure. However, in the initial stage of exposure, the SSF CI-6 does not show an effect of formation of a resistive film on the surface. The potentiodynamic polarization measurements suggest that, SSF CI-1 and SSF CI-2 are anodic type inhibitor, SSF CI-4 is cathodic type inhibitor, and SSF CI-5 and SSF CI-6 are mix type inhibitor. Moreover, the inhibitors tested show a similar corrosion inhibition effect as mussel adhesive protein (MAP) at the low dosage level.
287

Metal release of stainless steel particles in artificial lung fluid: complexation and synergistic effects / Frigörelse av metaller från partiklar av rostfritt stål i artificiell lungvätska: komplexering och synergieffekter

Liu, Yi January 2011 (has links)
Numerous metal release data have been published by the Div. Surface and Corrosion Science and the AISI 316L stainless steel particles’ behavior in artificial lysosomal fluid (ALF). This study aims to evaluate the effect of chemical components in ALF on metal release from stainless steel particles with a bottom-up methodology. Two sizes of 316L stainless steel particles were used to assess the particle size influence on the metal release in detail. The results show that organic complexing agents e.g. lactate, tartrate and citrate are responsible for the high metal release rate in ALF. Correlations between the metal release rate and the number of carboxyl groups of the organic ligand were observed. Moreover, metal release data in this study indicates no synergistic effects in ALF solution, and continued research is on-going to study the synergistic effects further. No quantitative rules of iron, chromium and nickel release from the same stainless particles could be found which may indicate that these metals are released through different pathways e.g. diffusion or chemical dissolution. In different solutions with different chemical components, one or more metal release mechanisms dominate over others and make the metal release rate unpredictable.
288

Radiation induced corrosion of copper / Strålningsinducerad korrosion av koppar

Björkbacka, Åsa January 2011 (has links)
The Swedish concept for storage of highly radioactive spent nuclear fuel is called the KBS-3 program. The proposed procedure is that the waste will be stored in a deep repository, 500 meters down in the Swedish bedrock, for 100 000 years. The fuel will be sealed inside cast iron cylinders surrounded by copper. The iron-copper canisters will then be placed one by one in holes and embedded in bentonite clay. The environment in the deep repository will be that of an underground rock cave, there will be groundwater and low amounts of oxygen present. Substances which are likely to react with the copper canister and cause corrosion are oxygen, sulphides and reactive water radiolysis products. Gamma radiation from the spent nuclear fuel will penetrate through the canister and further into the bentonite clay. When the gamma radiation comes in contact with the water in the bentonite clay, water radiolysis will occur. Corrosive radiolysis products are for example hydroxyl radicals, solvated electrons and hydrogen peroxide. The main purpose of this work was to study the effect of gamma radiation on copper pieces, in an aqueous environment, both under oxic and anoxic conditions. The surfaces of the copper pieces were characterized using scanning electron microscopy (SEM) and infrared absorption spectroscopy (IRAS). The dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). A second study was also performed where the reactions of three different oxidants; hydrogen peroxide, permanganate and iridium hexachloride, were studied in the presence of copper in an inert environment. All of the reactions were studied spectrophotometrically and the dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). The SEM measurements showed corrosion products on the irradiated copper pieces both under oxic and anoxic conditions. Under anoxic conditions the corrosion products had a center of a small cavity which was surrounded by a larger, flat, circular area. From that area, wider cavities were spreading out in apparently random directions. SEM-EDS measurements detected oxygen on the surface of the corrosion products. ICP measurements of the water phase showed that the water from irradiated samples contained higher levels of copper than unirradiated samples. ICP measurements from the reactions of copper in the presence of oxidants showed that copper was only dissolved in the presence of iridium hexachloride. These results show that gamma radiation causes corrosion of copper in an aqueous environment, both under oxic and anoxic conditions. It can also be concluded that hydrogen peroxide is not the radiolysis product that causes the dissolution of copper when copper is irradiated in an aqueous and inert environment.
289

Kommunikativa aspekter av kollaborativt lärande i fysikundervisning : En analys av hur elever på svenska gymnasieskolor kommunicerar, positionerar, deltar och använder representationer vid smågruppsdiskussioner.

Sarling, Emil January 2022 (has links)
Diskrepansen mellan inställningen gentemot fysik hos elever på gymnasiet i Europa och Nordamerika och arbetsmarknadens krav på kompetens inom naturvetenskapliga ämnen skapar utmaningar inför framtiden. Inställningen gentemot fysik har visat sig förbättras genom användandet av kollaborativt lärande och representationer. Rapporten syftar till att analysera svenska gymnasieelevers kommunikation i relation till deras identitet som fysiker samt hur de använder olika fysikaliska representationer i en kollaborativ kontext. Datan har insamlats genom gruppdiskussioner där elever tre och tre tillsammans löser kontextrika problem. Det visar sig att den matematiska representationen används frekvent och har en stark ställning i samtalen medan andra representationer som grafer och figurer snarare ses som hjälpmedel för lösningen. Den matematiska representationen ger även upphov till att respondenterna positionerar sig i samtalen som experter. Resultaten stärker tidigare forskningsresultat som påvisar matematikrepresentationens frekventa användning. / The discrepancy between the attitudes that students in upper secondary school has towards physics as a subject in Europe and North America and the labor market requirements of competence in science and technology creates challenges for future generations. The attitudes towards physics have shown to improve when different educational approaches of teaching, such as collaboration and the use of multiple representations have been applied. This report aims to analyse students in Swedish upper secondary schools communication in relation to their physics identity, as well as how they use multiple representations in a collaborative context. To analyse these relations, data has been gathered through group discussionss where students are encouraged to solve context-rich problems collaboratively. My findings shows that the mathematical representation is the most frequently used and also have a dominant position in relation to other representations such as graphs and figures, which are seen predominantly as an aid in forming the solution. When the students in the study utilize the mathematical representation they also tend to position themselves as experts. The findings are in line with previous research which have studied how students use multiple representations.
290

Tsirelson's Bound : Introduction and Examples / Tsirelson's gräns : Introduktion och Exempel

Kaarna, Amanda January 2022 (has links)
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. / Tsirelson's gräns är den övre gränsen till en Bell olikhet som är giltig för alla kvantmekaniska system. Vi diskuterar varför Tsirelson's gräns togs fram genom att titta på histroiska argument i kvantfysik, så som Einstein-Podolsky-Rosen (EPR) paradoxen, ett argument som säger att den kvantmekaniska beskrivningen av den fysikaliska verkligheten är offulständig, och lokala gömda variabler. Vi presenterar motargumentet till dessa teorier, Bell's olikheter, som senare generaliserades för att betyda alla olikheter som lokala system uppfyller, men som ett system i kvantsammanflättning kan bryta. Vi presenterar beviset för två specifika Bell olikheter: CHSH olikheten och I3322 olikheten. Sedan bevisas Tsirelson's gräns för CHSH olikheten med ett enkelt system av två sammanflättade spin-1/2 partiklar och ett generellt argument som stämmer för alla sammanflättade system. Vi ger den övre kvant gränsen för den generaliserade Clauser-Horne-Shimony-Holt (CHSH) olikheten, som beskriver situationen då vi har flera valmöjligheter för mätningar, genom att använda semidefinit programmering. Vi bevisar Tsirelson's gräns för I3322 olikheten genom att använda maximalt sammanflättade system och semidefinit programmering. Till slut diskuterar vi de övre gränserna som har erhållits ifrån de olika metoderna.

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