Abstract In this thesis oxidation of a pure and alloyed Cu surface was studied using density functional theory based calculations. The mechanism and energetics behind experimentally observed missing row reconstruction on a pure Cu(100) surface were studied. Examination of the formation of the missing row was approached by studying the profitableness of vacancy formation to the surface at oxygen coverages below and equal to 0.5 ML. However, an ideal surface was in all cases more favourable in energy than vacancy included structures. Therefore an additional Cu atom was added to the simulation cell to promote vacancy formation. A consequence of this on-surface Cu addition was the identifying of a new energetically favoured Cu-O-Cu chain formation. This newly identified structure is a possible transition state in the path from an ideal surface to a reconstructed one. Copper(I)oxide formation through sub-surface adsorption was examined on a reconstructed Cu(100) surface. At low O coverage on-surface adsorption was found to be much more favoured than adsorption on sub-surface sites. However, when coverage increased to 0.75 ML structures with both on-surface and sub-surface adsorbates possessed the lowest energy. Furthermore, the diffusion barriers to the sub-surface adsorption sites were low. Both these facts support the conclusion that the transition from the reconstructed missing row structure to the copper(I)oxide takes place without any large energy effort. The adsorption induced segregation of copper on a Ag/Cu(100) surface was studied by calculating the surface energies of slabs where the silver layer was positioned at different depths with varying O coverage. In addition, the segregation energies were also calculated with two Ag compositions. It was discovered that without oxygen adsorbates silver atoms lying on top of the surface were favoured but the surface segregation probability of Cu increases with increasing O coverage. The same calculation procedure was expanded to study the segregation probability of five additional alloy metals with a Cu surface. Without oxygen present Mg, Al and Zn possess a weak tendency to segregate to the surface, however, V and Cr prefer to stay in the bulk. The addition of oxygen adsorbates on the surface causes the segregation of all the dopants to the top of the surface. With the Al dopant the effect of the surface orientation and the oxygen coverage were also studied. The bonds between adsorbates and the surface were strongest with the densest surface, (111), and weakest with the most opened surface, (110). Furthermore, the enrichment probability was largest in the case of the (111) surface and lowest with the (110) surface. Probability increased with increasing oxygen coverage. / Tiivistelmä Tässä väitöstyössä on tutkittu puhtaan ja seostetun kuparipinnan hapettumista tiheysfunktionaaliteoriaan perustuvilla laskuilla. Kokeellisesti Cu(100) pinnan on havaittu rekonstruoituvan hapen vaikutuksesta. Rekonstruoitumisen aikana ideaalisesta pinnasta irtoaa joka neljäs pintakuparirivi ja muodostuu niin kutsuttu missing row- rakenne. Tämän rakenteen muodostumismekanismia ja muodostumiseen kuluvaa energiaa tutkittiin vertaamalla pintavakansillisten rakenteiden pintaenergioita vastaaviin ideaalipinnan arvoihin vaihtelevalla happipeitolla. Koska ideaalipinta oli kaikilla peittoasteilla energeettisesti suotuisampi kuin vakanssirakenne, yksittäisiä kupariatomeja lisättiin pinnalle stabiloimaan vakanssirakenteita. Kuparilisäyksen seurauksena löydettiin uusi energeettisesti edullinen Cu-O-Cu ketjurakenne. Tämä rakenne on mahdollinen ideaalisen ja rekonstruoituneen pinnan välinen siirtymätila. Kupari(I)oksidin muodostumista pinnanalaisen happiadsorption kautta tutkittiin rekonstruoituneella Cu(100) pinnalla. Pienillä happi-peittoasteilla pinnanpäällisen adsorption havaittiin olevan huomattavasti suotuisampaa kuin pinnanalaisen adsorption. Kuitenkin happi peiton kasvaessa 0,75 ML:iin rakenteet, joissa oli adsorbaatteja sekä pinnan alla että päällä, tulivat muita suotuisimmiksi. Myös lasketut energiavallit hapen diffuusiolle pinnalta pinnan alle olivat hyvin pieniä. Kaikki tulokset viittaavat siihen, että rekonstruoitunut Cu(100) pinta hapettuu helposti kupari(I)oksidiksi. Happiadsorption aikaansaamaa kuparin rikastumista (segregaatio) hopeakupariseosmetallin pinnalle tutkittiin laskemalla vaihtelevilla happipeitoilla pintaenergiat kuparipinnoille, joissa ensimmäinen, toinen ja kolmas kuparikerros oli korvattu hopealla. Myös segregaatioenergiat laskettiin kahdella eri seoskoostumuksella. Saatujen tulosten mukaan ilman happiadsoptiota hopea segregoituu pinnalle, kun taas hapen peittoasteen kasvaessa kupari rikastuu pinnalle. Samaa tutkimustapaa käytettiin myös tarkasteltaessa viiden muun seosmetallin segregaatiotodennäköisyyttä kuparipinnalla. Ilman pintahappea magnesiumilla, alumiinilla ja sinkillä oli heikko taipumus rikastua pinnalle, kun taas vanadium ja kromi pysyivät syvemmällä metallissa. Sen sijaan happea lisättäessä kaikki tutkitut seosmetallit pyrkivät siirtymään kohti pintaa. Myös hapen peiton sekä pintaorientaation vaikutusta segregaatioon tutkittiin hopeakuparipinnalla. Sekä happiadsorbaattien ja pinnan välinen sidos että segregaatiotodennäköisyys oli sitä voimakkaampaa, mitä tiheämmästä pinnasta oli kyse. Segregaatiotodennäköisyys kasvoi pinta-adsorption lisääntyessä.

Flow of granular materials is usually initiated when the shear stress is large enough and exceeds certain critical value. This can result in the presence of the dead-zones in which the flow itself does not take place. Motions of such materials are frequently described by Bingham model. Flows of granular fluids are frequently connected with the presence of free surface. In the thesis Bingham model is incorporated into a more general framework of Bingham-Korteweg fluids, which is a suitable way how to transfer free- boundary problems into the problems on fixed domains. A part of the thesis concerns mathematical analysis of interesting relevant problems for incompressible fluids. 1

This study explores the use of computer simulations to supplement learning in Science lessons, specifically the photoelectric effect. This study uses the Felder and Silverman Learning Style Model (FSLSM) as a theoretical framework to investigate the use of simulations as it provides a useful lens through which to explore the consistent way in which a person learns regardless of the teaching method or content learnt. Using this theoretical framework, this research investigates the experiences of learners with different learning styles when an interactive computer simulation is used to aid teaching the photoelectric effect in Physical Science. This case study used qualitative data collected from 17 computer literate Grade 12 learners in three different classes at a secondary school in Nelspruit, Mpumalanga. Analysis of the data collected in this study shows that when the simulation is used in Science, the learning experience of the learners is enhanced. Positive experiences for all four the Dimensions in the FSLSM could be indentified when the ICS was used and this could be linked to specific learning styles. Sensory and Intuitive learners enjoyed conducting the experiment that would normally require unsafe conditions and that the experiment could be set up quickly and with ease. The different dimension brought about by using the ICS was enjoyed by Intuitive learners. The visualisation of the abstract physical systems enhanced the learning for Visual and Verbal learners, whilst Global and Sequential learners felt that they gained a deeper understanding of the photoelectric phenomenon by using the ICS. Reflective learners enjoyed the precision of their pseudo-experimental data, but the Active learners felt that they did not understand the graphs given in the ICS. The interactive control variables and the fact that the learners had an option to work in either a group or on their own, benefitted both Active and Reflective learners. / Dissertation (MEd)--University of Pretoria, 2014. / gm2014 / Science, Mathematics and Technology Education / unrestricted

O presente trabalho tem por objetivo a caracterização dinâmica dos sistemas múltiplos de planetas extrassolares. O critério de classificação escolhido é baseado na proposta publicada inicialmente em Ferraz-Mello et al. (2005) e posteriormente modicada em Michtchenko et al. (2007). Para a obtenção dos parâmetros planetários orbitais foi feita uma pesquisa em diversos catálogos e artigos disponíveis para posterior criação de um catálogo próprio. Este incluiu somente sistemas extrassolares múlltiplos, ou seja, sistemas que contêm dois ou mais planetas orbitando a estrela. Foram feitas simulações numéricas de estabilidade dinâmica dos sistemas do catálogo próprio com tempos de integração de 200 mil até 21 milhões de anos. Ao todo, foram analisados 37 sistemas múltiplos extrassolares, divididos em 50 subsistemas considerando-se a estrela e dois planetas em órbitas consecutivas. Ao todo, foram analisados 37 sistemas múltiplos extrassolares, divididos em 50 subsistemas considerando-se a estrela e dois planetas em órbitas consecutivas. Estes foram submetidos ao total de 68 simulações computacionais. Os sistemas que apresentaram um cenário de estabilidade dinâmica foram posteriormente separados em três classes: ressonantes, seculares ou hierárquicos. Mais ainda, o comportamento secular desses sistemas foi classificado conforme o movimento do ângulo \"Deltavarpi\" : oscilatório em torno de 0º, oscilatório em torno de 180º ou circulatório. Os resultados das simulações são mostrados para todos os sistemas estudados. / The aim of the present work is a dynamic classification of multiple extrasolar systems. The characterization criterion used is based on a criterion proposed initially in Ferraz-Mello et al. (2005) and modified in Michtchenko et al. (2007). To obtain orbital parameters of the extrasolar systems, a search was done into several available catalogues and the scientific literature. A new catalogue was compiled containing only multiple extrasolar systems, that is, systems with two or more planets in orbit of the host star. Numerical simulations of dynamical stability of the cataloged systems were done considering pairs of planets on the consecutive orbits. Totally, 37 multiple extrasolar systems were analyzed, decomposed in 50 sub-systems each one consisting of the host star and two planets. The time evolution of those were simulated over time spans from 200 thousand years to 21 million years in 68 numerical simulations. The systems which have presented a dynamical stability were subsequently classified in resonants, secular or hierarchical and their secular behavior was classified with respect of the angle \"Deltavarpi\" as oscillation around 0º, oscillation around 180º or circulation. The result of all simulations are presented here for the analyzed systems.

The study investigated the impact of computer simulations on the teaching and learning of electromagnetism in grade 11. Electromagnetism is a section of the Physical Science curriculum. Two grade 11 classes in the Mgwenya circuit in Mpumalanga province of South Africa were used as a case study. Using a pre-test, post-test non-equivalent control group design, it was found that learners in the experimental group (n = 30) who were taught using the simulations achieved significantly higher scores on the post-test than learners in the control group (n = 35) who were taught using traditional teacher-centred teaching method; (t statistic = 3.582, df = 56, p<0.05). Learners were more active during the lessons, predicting, observing, discussing and explaining concepts. The use of simulations also provided support (scaffolding) that the learners need to enhance learning. The Hake’s normalized gain for the experimental group <g> = 0.32 compared to <g> = 0.18 for the control group confirmed conceptual improvement. Both teachers and learners indicated that they accept the use of computer simulations in teaching and learning of electromagnetism. / Science and Technology Education / M. Sc. (Mathematics, Science and Technology Education)

This study explores the use of computer simulations to supplement learning in Science lessons, specifically the photoelectric effect. This study uses the Felder and Silverman Learning Style Model (FSLSM) as a theoretical framework to investigate the use of simulations as it provides a useful lens through which to explore the consistent way in which a person learns regardless of the teaching method or content learnt. Using this theoretical framework, this research investigates the experiences of learners with different learning styles when an interactive computer simulation is used to aid teaching the photoelectric effect in Physical Science. This case study used qualitative data collected from 17 computer literate Grade 12 learners in three different classes at a secondary school in Nelspruit, Mpumalanga. Analysis of the data collected in this study shows that when the simulation is used in Science, the learning experience of the learners is enhanced. Positive experiences for all four the Dimensions in the FSLSM could be indentified when the ICS was used and this could be linked to specific learning styles. Sensory and Intuitive learners enjoyed conducting the experiment that would normally require unsafe conditions and that the experiment could be set up quickly and with ease. The different dimension brought about by using the ICS was enjoyed by Intuitive learners. The visualisation of the abstract physical systems enhanced the learning for Visual and Verbal learners, whilst Global and Sequential learners felt that they gained a deeper understanding of the photoelectric phenomenon by using the ICS. Reflective learners enjoyed the precision of their pseudo-experimental data, but the Active learners felt that they did not understand the graphs given in the ICS. The interactive control variables and the fact that the learners had an option to work in either a group or on their own, benefitted both Active and Reflective learners. / Dissertation (MEd)--University of Pretoria, 2013. / gm2014 / Science, Mathematics and Technology Education / unrestricted

We present two possible thermodynamical approaches towards a derivation of a model, proposed by Korteweg at the beginning of the 20th century, that is suitable to describe phase transitions liquid-vapor with non-sharp interfaces. The first approach (Dunn, Serrin (1985)) is based on classical rational continuum thermodynamics. The second approach (Heida, Málek (2010)) stems from the principles of classical nonequilibrium continuum thermodynamics. We compare both approaches in favor of the second one. The considered constitutive equation for the Cauchy stress is nonlinear. Nonlinearity and higher order derivatives of the density makes the analysis of relevant problems for the Navier-Stokes- Korteweg (NSK) fluid more difficult in comparison to problems concerning Navier-Stokes equations. Special attention is devoted to the appropriate choice of the boundary conditions. We also investigate the influence of compressibility on the stability of bubbles by comparing numerical simulations for compressible NSK fluid and its incompressible variant. Instabilities observed for a compressible NSK fluid are due to the pressure that has a different meaning for incompressible fluid. Powered by TCPDF (www.tcpdf.org)

Recent experimental studies indicate that polymeric structures with a well-adjusted balance of amphiphilic parts may translocate through self-assembled phospholipid bilayers and enhance the passive trans-membrane transport of smaller molecules. Using a coarse grained lattice Monte Carlo model with explicit solvent we investigate self-assembled lipid bilayers interacting with a linear polymer chain under variation of the hydrophobicity of the chain. Here, we focus on the relationship between the chain's hydrophobicity and its translocation behavior through the membrane as well as induced membrane perturbations. We show, that there is an adsorption transition of the polymer at the bilayer interface, where effectively the solvent phase and the tail phase of the bilayer are equally repulsive for the polymer. Close to this adsorption threshold of the polymer both the translocation probability of the polymer as well as the permeability of the membrane with respect to solvent are enhanced significantly. The frequency of polymer translocation events can be understood quantitatively assuming a simple diffusion along a one-dimensional free energy profile, which is controlled by the effective lipophilicity of the chain and the tail-packing in the bilayer's core. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

We report a class of the mathematics in which an animation technology (calculating and plotting capabilities) of the software Mathematica is utilized. This class is taught for university students in a computer laboratory during a second semester. It is our purpose to make a student realize the usefulness and the importance of mathematics easily through visualization. In addition, we hope that students will acquire a new power of mathematics needed in the 21st century. For several years, we have continued this kind of class, and have continued to investigate the effectiveness that our teaching method (especially visualization) brings in the understanding of the mathematics. In this paper, we present some of this teaching method, which is performed in our class. From the questionnaire survey, it is found that our teaching method not only convinces students that the mathematics is useful or important but also deepens the mathematic understanding of students more.

Detta arbete syftar till att utveckla ett förslag på ett utbildningsmaterial i form av en programmeringsorienterad fysik- och matematiklaboration. Målgruppen är i förstahand studenter som läser andra terminen i det ingenjörsförberedande programmet Tekniskt basår (KTH), men även studenter på motsvarande kunskapsnivå (tillexempel elever i gymnasiets naturvetenskapliga program). Laborationen konstruerades för att skapa förutsättningar för studenterna att:1) Visa på kritiskt tänkande,2) visa på kollaboration,3) öka ämnesförståelsen. Det föreslagna utbildningsmaterialet omfattar området beräkningsfysik, där en ickelinjärdifferentialekvation härled från en matematisk pendel ska lösas med hjälp avnumeriska metoder. Laborationens uppgifter formulerades med kritiskt tänkande som utgångspunkt och utfördes med parprogrammering som samarbetsform för kollaboration. I detta arbete undersöktes punkter 1) och 2) i en utbildningssituation med elever från andra terminen på Tekniskt basår. Fyra elevgruppers konversationer spelades in och en innehållsanalys utfördes på transkriberingen av ljudinspelningen. En mönsterjämförelsemetod användes för att stärka slutsatserna. Utifrån resultaten av undersökningsprojektet konstaterade vi att den teoretiska propositionen om att laborationskonstruktionen har medverkat till elevernas kollaboration och appliceringav kritiskt tänkande, har stärkts. / This work aims to develop a proposal for educational material in the form of a programming-oriented Physics and Mathematics lab. The target group is mainly students from the second semester in the Technical Preparatory Year program (KTH), but also students of equivalent knowledge level (for example, students in the upper secondary school- natural science program). The lab was designed to create opportunity for students to:1) apply critical thinking, 2) demonstrate collaboration, 3) increase subject understanding. The proposed educational material comprises computational physics, where a non linear differential equation derived from a mathematical pendulum is solved using numerical methods. The exercises in the lab were formulated with critical thinking in mind and pair programming was used as the context for collaboration. In this paper 1) and 2) were investigated in an educational setting with students from the second semester of the Technical Preporatory Year (KTH). The conversations of four student groups were recorded and a content analysis was performed on the transcriptions of the audio recordings. A pattern matching method was used to strengthen the conclusions. Based on the results of the research project, we found that the theoretical proposition that the construction of the laboratory work has contributed to the collaboration and application of critical thinking by the students,has been strengthened.