Στην παρούσα εργασία παρουσιάζεται μία μέθοδος πλήρους διακριτοποίησης (χωρικής και χρονικής) για την εξίσωση των Korteweg και de Vries. H μέθοδος αυτή μελετήθηκε από τον J. Schiff στην εργασία Loop groups and discrete KdV equations και στηρίζεται στην διάσπαση Birkhoff σε κατάλληλη ομάδα βρόχων για την εύρεση του ζεύγους Lax. Για τις προκύπτουσες εξισώσεις μερικών διαφορών κατασκευάζονται μετασχηματισμοί Backlund μέσω της ίδιας μεθόδου, οι οποίοι, στην συνέχεια, χρησιμοποιούνται για την εύρεση σολιτονικών λύσεων. Ειδικότερα, μία από τις διακριτοποιήσεις έχει άμεσο ("φυσικό") συνεχές όριο την εξίσωση potential KdV. Σε κάθε περίπτωση διακριτοποίησης, κατασκευάζονται σολιτονικές λύσεις, οι οποίες συγκρίνονται με αυτές της συνεχούς περίπτωσης και εξετάζονται ως προς την σολιτονική αλληλεπίδραση. / In this thesis, we present a method of full discretization (both spatial and temporal coordinates are discretized) for the Korteweg and de Vries' equation. This method was studied by J. Schiff in his paper Loop groups and discrete KdV equations. The procedure is based on Birkhoff decomposition in an appropriate loop group in order to derive a Lax representation. For the resulting partial difference equations, we construct Backlund transformations via the same method, which are used to generate soliton solutions. In particular, one discretization has the potential KdV equation as a standard (natural) continuum limit. In both cases, soliton solutions are produced and compared with those of the continuous case. Finally, we study their soliton interaction.

Saving energy in buildings is of great importance because about 30 to 40 % of the energy in the world is used in buildings. An electrochromic window (ECW), which makes it possible to regulate the inflow of visible light and solar energy into buildings, is a promising technology providing a reduction in energy consumption in buildings along with indoor comfort. A polymer electrolyte is positioned at the center of multi-layer structure of an ECW and plays a significant role in the working of the ECW. In this study, polyethyleneimine: lithium (bis(trifluoromethane)sulfonimide (PEI:LiTFSI)-based polymer electrolytes were characterized by using dielectric/impedance spectroscopy, differential scanning calorimetry, viscosity recording, optical spectroscopy, and electrochromic measurements. In the first part of the study, PEI:LiTFSI electrolytes were characterized at various salt concentrations and temperatures. Temperature dependence of viscosity and ionic conductivity of the electrolytes followed Arrhenius behavior. The viscosity was modeled by the Bingham plastic equation. Molar conductivity, glass transition temperature, viscosity, Walden product, and iso-viscosity conductivity analysis showed effects of segmental flexibility, ion pairs, and mobility on the conductivity. A connection between ionic conductivity and ion-pair relaxation was seen by means of (i) the Barton-Nakajima-Namikawa relation, (ii) activation energies of the bulk relaxation, and ionic conduction and (iii) comparing two equivalent circuit models, containing different types of Havriliak-Negami elements, for the bulk response. In the second part, nanocomposite PEI:LiTFSI electrolytes with SiO2, In2O3, and In2O3:Sn (ITO) were examined. Adding SiO2 to the PEI:LiTFSI enhanced the ionic conductivity by an order of magnitude without any degradation of the optical properties. The effect of segmental flexibility and free ion concentration on the conduction in the presence of SiO2 is discussed. The PEI:LiTFSI:ITO electrolytes had high haze-free luminous transmittance and strong near-infrared absorption without diminished ionic conductivity. Ionic conductivity and optical clarity did not deteriorate for the PEI:LiTFSI:In2O3 and the PEI:LiTFSI:SiO2:ITO electrolytes. Finally, propylene carbonate (PC) and ethylene carbonate (EC) were added to PEI:LiTFSI in order to perform electrochromic measurements. ITO and SiO2 were added to the PEI:LiTFSI:PC:EC and to a proprietary electrolyte. The nanocomposite electrolytes were tested for ECWs with the configuration of the ECWs being plastic/ITO/WO3/polymer electrolyte/NiO (or IrO2)/ITO/plastic. It was seen that adding nanoparticles to polymer electrolytes can improve the coloring/bleaching dynamics of the ECWs. From this study, we show that nanocomposite polymer electrolytes can add new functionalities as well as enhancement in ECW applications.

In this work we report on two sets of measurements involving the Hall-B photon tagging system of the Tomas Jefferson National Accelerator Facility. The relative energy calibration of the tagging counters was performed by using the PrimEx pair spectrometer and a series of high position resolution micro-strip detectors. The photon energies were determined by forming coincidence between the tagger and the e+ e- pairs for several values of the pair spectrometer magnetic field between 0.36T to 1.9T (total of 180 fields). The second set of measurements, collected in conjunction with the Fall 2004 PrimEx run, investigated inherent limitations on the photon tagging technique. We report for the first time an experimental signature for these effects.

Metacognition in collaborative learning settings is an emerging topic in research on metacognition. This study focused on the development of metacognitive skills during pair programming in order to enhance knowledge productivity. Pair programming entails collaboration between two programmers, each fulfilling a specific role during the execution of the programming task, and has recently been used in educational contexts as a teaching and learning strategy to improve learning in computer programming (DeClue, 2003:49; Preston, 2006b:16). In this study the outcomes of collaborative learning during pair programming are referred to as knowledge productivity, which is measured against the criteria of enhanced knowledge construction, enhanced problem-solving skills, conceptual changes in individual perspectives, commitment to work with the other member of the pair, and application of the results of the learning process (Tillema & Van der Westhuizen, 2006:51,55). To investigate the influence of a metacognitive teaching and learning approach to pair programming on knowledge productivity, a repeated-measures experiment with a control group was conducted among a number of Grade 11 learners who had been implementing pair programming in the learning of Information Technology at secondary school level. At the beginning of the study both groups completed two questionnaires, one on metacognition and the other on knowledge productivity. At the same stage, a number of randomly selected participants from each group were interviewed on the same two topics, using a semi-structured interview approach. This procedure was repeated three months later, without any intervention. During the intervention phase, the experimental group implemented a set of self-directed metacognitive questions that they had to answer while doing a pair programming task. These self-directed metacognitive questions form part of a metacognitive teaching and learning strategy suggested by the researcher. The members of the experimental group also kept a journal to describe how the self-directed questions directed their thinking during the execution of the pair programming task. At the end of the experimental period, the mo questionnaires on metacognition and knowledge productivity were completed by both groups again, supported by the interviews of the same selected participants. The results derived from the empirical study showed that the knowledge productivity of learners programming in pairs can be enhanced by implementing a metacognitive teaching and learning strategy. The metacognitive teaching and learning strategy implemented during this study was then adapted to make it suitable for use by teachers and learners during pair programming. / Thesis (Ph.D. (Education)--North-West University, Potchefstroom Campus, 2010.

Metacognition in collaborative learning settings is an emerging topic in research on metacognition. This study focused on the development of metacognitive skills during pair programming in order to enhance knowledge productivity. Pair programming entails collaboration between two programmers, each fulfilling a specific role during the execution of the programming task, and has recently been used in educational contexts as a teaching and learning strategy to improve learning in computer programming (DeClue, 2003:49; Preston, 2006b:16). In this study the outcomes of collaborative learning during pair programming are referred to as knowledge productivity, which is measured against the criteria of enhanced knowledge construction, enhanced problem-solving skills, conceptual changes in individual perspectives, commitment to work with the other member of the pair, and application of the results of the learning process (Tillema & Van der Westhuizen, 2006:51,55). To investigate the influence of a metacognitive teaching and learning approach to pair programming on knowledge productivity, a repeated-measures experiment with a control group was conducted among a number of Grade 11 learners who had been implementing pair programming in the learning of Information Technology at secondary school level. At the beginning of the study both groups completed two questionnaires, one on metacognition and the other on knowledge productivity. At the same stage, a number of randomly selected participants from each group were interviewed on the same two topics, using a semi-structured interview approach. This procedure was repeated three months later, without any intervention. During the intervention phase, the experimental group implemented a set of self-directed metacognitive questions that they had to answer while doing a pair programming task. These self-directed metacognitive questions form part of a metacognitive teaching and learning strategy suggested by the researcher. The members of the experimental group also kept a journal to describe how the self-directed questions directed their thinking during the execution of the pair programming task. At the end of the experimental period, the mo questionnaires on metacognition and knowledge productivity were completed by both groups again, supported by the interviews of the same selected participants. The results derived from the empirical study showed that the knowledge productivity of learners programming in pairs can be enhanced by implementing a metacognitive teaching and learning strategy. The metacognitive teaching and learning strategy implemented during this study was then adapted to make it suitable for use by teachers and learners during pair programming. / Thesis (Ph.D. (Education)--North-West University, Potchefstroom Campus, 2010.

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This thesis focuses on the development of a distributed pair programming tool that enables two programmers to generate code together in JBuilder editor over the web. First, software development processes are generally reviewed and Extreme Programming, Distributed Extreme Programming, and Distributed Pair Programming issues are examined. The tools that enable Distributed Pair Programming are compared. This thesis also specifies the functional requirements of the newly presented tool and includes information about its design and implementation processes. Finally, an evaluation is given by indicating the positive and negative sides of the tool.

This thesis reports progress in three major aspects of σ-bonded organometallic porphyrins that are described in the published papers found in chapters 4, 5 and 6. meso-Iodoporphyrins, which were prepared in a rapid, selective and high yielding methodology from the respective 1-palladioporphyrins or bromoporphyrins, are important starting materials for further functionalisations of porphyrins. Their utility was confirmed in a palladium-catalysed coupling reaction and this novel synthetic strategy could potentially be applied for iodine/bromine exchange on other organic substrates.. A 1-palladioporphyrin was also utilised to optimise the reaction conditions leading to the formation of porphyrinylphosphine oxides. This synthetic strategy simplified the challenging optimisation of the palladium-catalysed reaction and has great potential to be applied in other catalytic processes. Subsequently a suite of porphyrinylphosphine oxides was prepared under the optimised catalytic conditions. These macrocycles, which represent a new class of porphyrins, were isolated cleanly in very high yields. Detailed spectroscopic investigations as well as X-ray single crystal analysis demonstrated their structures unambiguously and established their potential as ligands for supramolecular chemistry. The coordinating properties of phosphine oxides in general and porphyrinylphosphine oxides in particular, towards Mg(II) centred porphyrins were examined in further experiments. Triphenylphosphine oxide showed a strong affinity towards Mg(II) porphyrins and the calculated displacement constant of 5.3 × 105 M-1 was two orders of magnitude larger than any other Mg(II) porphyrin-ligand binding constant reported thus far. Di- and triporphyrin arrays consisting of Mg(II) porphyrin coordinated to free base and Ni(II) porphyrinyl mono- and bis-phosphine oxides were also prepared in high yields. Spectroscopic studies indicated that these porphyrin oligomers exhibit strong inter-porphyrin electronic interaction. A Mg(II) porphyrinylphosphine oxide dimer was also isolated in a satisfactory yield. The large self-association constant of 5.5 × 108 M-1 confirmed the strong affinity of porphyrinylphosphine oxides towards Mg(II) porphyrins and established these complexes as the first strongly bound synthetic Mg(II) porphyrin analogues of the "special pair" of the photosynthetic reaction centre.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 6 uppsatser.