Since the development of the ruthenium containing precatalysts Grubbs 1 (1) and Grubbs 2 (2), there was an increase in the development of new precatalysts. The NMR characterization could not cope with this. The NMR characterization mainly consists of 1H, 31P, COSY and rarely 13C. Due to the high natural abundance of 1H and 31P (99.98% and 100%), these experiments could be carried out quickly and easily. The only change that had to be made was to the spectral width, to accommodate the carbene signal (Ru=CH) between δ 20.02 and δ 17.32 ppm. The lack of 13C characterization is attributed to the low natural abundance of these nuclei that is only 1.10% and the lack of published parameters. Furthermore, the broad spectral width of 300 ppm increases the difficulty because the number of scans has to be increased to increase the sensitivity of the spectra and obtain useful data. In this study the precatalyst 1 was used to learn the NMR technique as well as to acquire the NMR parameters. 2 and two other commercial Grubbs-type precatalysts 3 and 4 underwent NMR characterization so that acquired values could be compared with the literature. Six other non-commercial Grubbs-type precatalysts 5-10 were synthesized and characterized. Due to the instability of the precatalysts and taking into account the duration of these experiments, the characterization was done over three steps. The first step was to do the following experiments: 1H, COSY, HSQC and HMBC, which took four hours. The next step was the DEPT135 experiment of three hours, and finally the 13C experiment of seven hours. The maximum amount of information could be obtained in this way. The combined NMR parameters for this study was obtained and used to characterize the Grubbs-type precatalysts 5-10 partially. Due to the large amount of overlapping peaks in the aromatic and alkane areas the resolution was not sufficient for full characterization. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Chapter 1 outlines the aim of the study, research methodology, delimitation of scope and the definition of some terms. This is followed by a list of Zulu short stories which Ntuli has already contributed. His other contributions in circles outside the writing of fiction are also acknowledged. Finally, tribute is paid to some contributions made by Ntuli as an endeavour to uplift the standard of Zulu writing. In Chapter 2 plot structure is discussed. This is followed by an in-depth semiotic analysis of some short stories. Chapter 3 deals with the different narration techniques employed by the author in his short stories. Chapter 4 differentiates between actors and characters. Different methods of character portrayal are investigated. Chapter 5 concludes this dissertation by summarising the main finding of this study. It also brings forth some conclusions with regard to literary merit of Ntuli's short stories and his contribution to Zulu literature. / African Languages / M.A. (African Languages)

Early written Shona narratives like Solomon Mutswairo's Feso [Thorn; name of main character, 1982] evince fantasy since they emanated from folktales, a genre that abounds in this element. Contrary to this, Charles Mungoshi attempts to portray life faithfully in Makunun'unu Maodzamwoyo [Brooding breeds despair, 1977], Ndiko Kupindana Kwamazuva [How time passes, 1975] and Kunyarara Hakusi Kutaura? [Is silence not a form of speech? 1983]. This study attempts to show how this realism manifests itself in the components that constitute each of the works: setting, plot, characterisation, theme and style. Mungoshi's characters, for instance, are not one-sided supernatural beings who perform fabulous acts. Instead, they have strengths and limitations like people in everyday life. Their actions and speech are consistent with their social backgrounds. By injecting realism into the Shona narrative, Mungoshi has contributed towards its development. Due to this realism, the works deserve the label "novels" as opposed to "romances". / African Languages / M.A. (African languages)

The future of human embryonic stem cell (hESC) research with regards to their applicability in a therapeutic setting, relies on the development and standardisation of consistent and robust methods to demonstrate their defining characteristics; their pluripotent ability to form all three germ layers and their capacity for self-renewal. Although much research has been carried out to investigate new methods of culturing hESCs, many of these studies have not robustly concluded the impact of prolonged culture on genetic and genomic stability nor have they examined in any comparative detail the impact of the culture conditions such as differences in feeders used or the media composition in which the stem cells are cultured in. The aim of this thesis therefore was to investigate and evaluate methods for improving the uniform and robust culture and characterisation of hESCs over prolonged periods in culture. Four hESC lines ( RH5, HUES9, SHEF1 and NCL5) were chosen on the basis that they had not previously been well characterised and therefore could potentially benefit the wider stem cell community by increasing diversity, rather than continue to use the already small subset of well publicised lines. The RH5, HUES9, SHEF1 and NCL5 cells were subjected to long term passaging using recombinant enzyme TrypLE™ Express, on human feeders, mouse feeders and feeder free matrix Matrigel in combination with defined media mTeSR1, for uniform scale up. Changes in characteristic stem cell surface markers were compared using two techniques; flow cytometry and quantitative in situ fluorescence microscopy. Genomic stability was assessed by real time PCR. Chromosomal integrity was monitored using array genomic hybridisation (aCGH). Array genomic hybridisation analysis of cells cultured for 20 passages by enzymatic passaging revealed changes in copy number variations in all the stem cell lines. Aberrations on chromosomes 12, 17 and 20, appeared most commonly as a result of long term culture. Although no significant differences were seen between hESCs cultured on mouse and human feeders, cultures on Matrigel showed fewer detected chromosomal aberrations. Expression of cell surface stemness markers SSEA3, SSEA4, TRA1-60 and TRA1-81 were maintained by hESC cultured on all matrices and confirmed by the use of flow cytometry and high throughput quantitative immunofluorescence imaging using the TissueFaxs™ cell analysis microscopy system. In depth imaging revealed subtle but important differences in the way in which hESCs attach and proliferate on different matrices. Genetic profiling of each of the stem cell lines using Taqman Low density array cards to assess the expression of 96 genes by Real Time PCR, demonstrated the continued expression of stemness genes 21 at late passage, and low level expression of differentiation genes, inherent to particular stem cell lines. Although both mouse and human feeders and Matrigel support the undifferentiated growth of hESCs, subtle differences from the hESCs were seen as a result of their use, most obviously, changes in morphology and how they proliferate. This was further explored in the stem cell line NCL5, as it demonstrated a readiness to adapt to new matrices, better chromosomal stability and higher expression of cell surface markers compared with the other hESC lines. Using in vitro differentiation assays to all three germ layers, NCL5 cultured to late passage (p+20) on human feeder iMRC5, mouse feeder iMEF and feeder free matrix Matrigel, demonstrated the ability to differentiate to ectoderm, endoderm and mesoderm progenitors after induction using three 7 day flat based directed differentiation protocols. Altered differentiation patterns were detected by Real Time PCR and TissueFaxs™ imaging and quantitative analysis, as a consequence of the prolonged culture on the specific matrices used. Such key findings allude to the strong influences of microenvironment and will help to improve the standardisation of in vitro differentiation assays. From these studies, chromosomal changes had no impact on NCL5 stem cell lines‘ ability to form progenitors, however small genetic instabilities may still play a role in terminal differentiation of germ lineage specific cell types. The findings of the programme of work described has led to the successful culture methods and characterisation testing validated in this project being incorporated into routine culture and banking of research grade hESCs at the UK Stem Cell Bank. These protocols will now be made more widely available and should assist stem cell researchers in adopting the most suitable and optimum conditions for culturing stem cells in the undifferentiated and stable state. With the huge surge in stem cell research over the past decade, the development of robust characterisation and culture methods will undoubtedly have significant impact on the exploitation of these cells for regenerative medicine and to assist with this a future aim of the stem cell bank will be to standardise methodologies for clinical grade banking.

Polyethylene Terephthalate (PET) is one of the most important polymers in use today for packaging due to its outstanding properties. The usage of PET has grown at the highest rate compared with other plastic packaging over the last 20 years, and it is anticipated that the increase in global demand will be around 6% in the 2010-2015 period. The rheological behaviour, thermal properties, tensile modulus, permeability properties and degradation phenomena of PET/clay nanocomposites have been investigated in this project. An overall, important finding is that incorporation of nanoclays in PET gives rise to improvements in several key process and product parameters together - processability/ reduced process energy, thermal properties, barrier properties and stiffness. The PET pellets have been compounded with carefully selected nanoclays (Somasif MAE, Somasif MTE and Cloisite 25A) via twin screw extrusion to produce PET/clay nanocomposites at various weight fractions of nanoclay (1, 3, 5, 20 wt.%). The nanoclays vary in the aspect ratio of the platelets, surfactant and/or gallery spacing so different effect are to be expected. The materials were carefully prepared prior to processing in terms of sufficient drying and re-crystallisation of the amorphous pellets as well as the use of dual motor feeders for feeding the materials to the extruder. The rheological properties of PET melts have been found to be enhanced by decreasing the viscosity of the PET i.e. increasing the 'flowability' of the PET melt during the injection or/and extrusion processes. The apparent shear viscosity of PETNCs is show to be significantly lower than un-filled PET at high shear rates. The viscosity exhibits shear thinning behaviour which can be explained by two mechanisms which can occur simultaneously. The first mechanism proposed is that some polymer has entangled and few oriented molecular chain at rest and when applying high shear rates, the level of entanglements is reduced and the molecular chains tend to orient with the flow direction. The other mechanism is that the nanoparticles align with the flow direction at high shear rates. At low shear rate, the magnitudes of the shear viscosity are dependent on the nanoclay concentrations and processing shear rate. Increasing nanoclay concentration leads to increases in shear viscosity. The viscosity was observed to deviate from Newtonian behaviour and exhibited shear thinning at a 3 wt.% concentration. It is possible that the formation of aggregates of clay is responsible for an increase in shear viscosity. Reducing the shear viscosity has positive benefits for downstream manufacturers by reducing power consumption. It was observed that all ii three nanoclays used in this project act as nucleation agents for crystallisation by increasing the crystallisation temperature from the melt and decreasing the crystallisation temperature from the solid and increasing the crystallisation rate, while retaining the melt temperature and glass transition temperatures without significant change. This enhancement in the thermal properties leads to a decrease in the required cycle time for manufacturing processes thus potentially reducing operational costs and increasing production output. It was observed that the nanoclay significantly enhanced the barrier properties of the PET film by up to 50% this potentially allows new PET packaging applications for longer shelf lives or high gas pressures. PET final products require high stiffness whether for carbonated soft drinks or rough handling during distribution. The PET/Somasif nanocomposites exhibit an increase in the tensile modulus of PET nanocomposite films by up to 125% which can be attributed to many reasons including the good dispersion of these clays within the PET matrix as shown by TEM images as well as the good compatibility between the PET chains and the Somasif clays. The tensile test results for the PET/clay nanocomposites micro-moulded samples shows that the injection speed is crucial factor affecting the mechanical properties of polymer injection moulded products.

Notre travail s'inscrit dans le cadre des télécommunications par fibres optiques où l'information transite sous la forme d'impulsions lumineuses dans le guide d'onde que constitue la fibre. Face à la demande sans cesse croissante en matière de débit d'information transmise dans une fibre, les trains d'impulsions qui véhiculent cette information sont rendus plus denses : les impulsions sont plus brèves et la distance qui les sépare diminue. Cette évolution est freinée par deux aspects qui sont de natures très différentes. Le premier naît du besoin de diriger l'information dans un réseau, ce qui nécessite d'effectuer des opérations logiques et de passer par des dispositifs électroniques qui sont lents à l'échelle de l'optique. Le deuxième aspect consiste en la dispersion de la vitesse de groupe présente dans la fibre. Sous son infiuence, les impulsions ont tendance à s'étaler et peuvent se recouvrir au sein du train, ce qui détruit l'information.<br> La dispersion peut être contrée par la non-linéarité de la fibre optique. Celle-ci provoque l'effet inverse de la dispersion : une contraction de l'impulsion. Si l'on choisit judicieusement le profil des impulsions, elles peuvent se propager sans déformation grâce à la compensation des deux effets antagonistes que sont la dispersion et la non-linéarité. De telles impulsions sont appelées « solitons ». Ils sont stables et permettent de véhiculer l'information sans la détruire. Malheureusement, la nature non linéaire de leur régime de propagation implique qu'ils modifient le milieu supportant leur propagation au point d'interagir avec leurs voisins et de modifier leur instant d'arrivée en fin de fibre. Cet effet détériore l'information et oblige à espacer les impulsions qui transitent dans la fibre, ce qui limite le débit d'information véhiculée.<br> Jusqu'à présent, les effets non linéaires dans les fibres optiques ont principalement été étudiés dans une approximation scalaire de la réalité, ce qui ne permet pas de prédire un certain nombre de phénomènes qui font intervenir la polarisation du champ électrique associé à l'impulsion. Un modèle vectoriel permet, entre autres, de décrire les « solitons elliptiques fondamentaux », les « solitons de parois de domaines de polarisation » et les « états liés de solitons vectoriels ».<br> C'est à ces êtres optiques que nous nous sommes intéressés dans notre travail qui comprend trois grands axes.<br> Le premier consiste en une étude théorique des états liés de solitons vectoriels. Préalablement à notre étude, ceux-ci se sont révélés instables dans des simulations numériques. Nous avons abordé le problème de manière analytique et montré l'existence d'états liés de solitons vectoriels. Ensuite, nous avons étudié leur dynamique et montré qu'ils sont instables par brisure de symétrie dans les fibres optiques isotropes. Suite à cela, nous avons analysé leur propagation en fibres à biréfringence aléatoire et montré qu'ils y sont stables, ce qui a permis d'expliquer la réussite d'expériences de multiplexage en polarisation dans lesquelles deux impulsions successives du train peuvent être vues comme des états liés.<br> La formulation mathématique des états liés que nous avons étudiés dans les fibres optiques est analogue à celle des états liés spatiaux qui apparaissent dans les milieux de type Kerr. Cette analogie nous a permis de proposer un principe de commutation, basé sur l'instabilité des états liés par brisure de symétrie, qui présente les avantages de nécessiter une très faible puissance de contrôle et de travailler beaucoup plus rapidement que l'électronique.<br> Les deux autres axes de notre travail sont liés à l'observation expérimentale des solitons elliptiques parmi lesquels les « solitons de parois de domaines de polarisation » constituent de bons porteurs d'information dans les fibres optiques car, selon les simulations numériques, ils ne souffriraient pas des interactions entre solitons voisins d'un train telles que nous les avons décrites ci-dessus pour les solitons scalaires. Afin d'observer les solitons elliptiques, trois étapes sont nécessaires. D'un point de vue pratique, elles s'agencent comme suit : il faut vérifier qu'il existe des fibres dont l'isotropie soit suffisante pour soutenir leur propagation, puis il faut disposer des instruments qui permettent de les observer et, enfin, il faut les générer. Cette dernière étape mérite une étude complète à elle seule, et nous ne l'avons pas abordée.<br> Nous avons par contre vérifié la possibilité d'observer des phénomènes qui ne peuvent se produire qu'en fibres isotropes et qui trouvent leur origine dans le même phénomène physique, à savoir, l'interaction entre la dispersion et la non-linéarité vectorielle. En l'occurrence, nous avons effectué la première observation d'une prédiction effectuée il y a trente ans, mais jamais observée jusqu'alors : l'existence de l'« instabilité modulationnelle de polarisation » en fibre optique isotrope. La vérification de toutes les prédictions associées à cette instabilité nous a permis de conclure que le choix d'une fibre de type « spun » associé à des précautions d'utilisation permettra de propager des solitons elliptiques.<br> Suite à ce succès, nous avons abordé l'étude du dispositif de détection des solitons elliptiques. Pour comprendre sa spécificité, il faut savoir que l'observation des solitons elliptiques nécessite de travailler à des puissances de crête très élevées pour faire ressortir la non-linéarité de la fibre optique. Ces puissances sont atteintes en concentrant une faible énergie sur un temps ultracourt, de l'ordre d'une centaine de femtosecondes. Nous avons développé deux méthodes de mesure basées sur la reconstruction de la phase spectrale de l'impulsion au départ de signaux de battement entre fréquences voisines du spectre. Ces méthodes présentent l'avantage d'être purement linéaires, ce qui leur confère une très grande sensibilité ; et de permettre le calcul simple et sans ambiguïté de la phase spectrale. La première des techniques que nous avons développées est adaptée aux trains ultrarapides d'impulsions courtes et répond à un besoin dans le domaine des télécommunications, tandis que la seconde peut s'appliquer aux bas taux de répétitions et aux impulsions courtes ou ultracourtes.

Atherosclerotic plaques in the bifurcation of the carotid artery vessels can pose a significant stroke risk from stenosis, thrombosis and emboli, or plaque rupture. However, the possibility of the latter depends on the structure of the plaque and its stability. So far, the assessment of such depositions, and the evaluation of the risk they pose, is not satisfactory with 3 Tesla black blood imaging. It is expected that the SNR increase at 7 Tesla, together with an appropriate and patient-safe RF coil, will result in higher resolution images that would help in better assessing the composition of atherosclerotic plaques in vessel walls. A custom-built neck array was designed and constructed, with the aim of investigating the benefits of the higher field strength using DANTE-prepared black blood imaging. A 4-channel transmit array was designed to generate the required <b>B</b>^&plus;<sub style='position: relative; left: -.5em;'>1</sub> field for the DANTE module to be used. A separate close fitting 4-channel receive array was preferred for improved SNR and parallel (receive) imaging. Geometric, active, passive as well as preamp decoupling schemes were employed for adequate isolation between the arrays and their channels. Electromagnetic simulation software, Semcad X (SPEAG, Zurich), was used for safety assessment with human phantoms (Virtual population). The <b>E</b> fields for 1 W transmission per channel were calculated for each element for a worst case SAR estimation. The transmission power limits per channel were set according to the 10g SAR limit set in IEC 60601. For simulation validation, temperature measurements and surface heat mapping were performed on a meat phantom. Finally, a healthy male subject was scanned using a protocol consisting of <b>B</b>₁ mapping, RF shimming at an ROI, and 2D and 3D DANTE prepared Gradient Echo (GRE). The worst-case heating scenario, as defined in the methods section, generated a maximum local SAR of 7.65 W/kg for 1 Watt per channel input. Thus, for 1st level mode (20W/kg max), the power limit was set at 2.6 W per channel. The heating profile was similar to that simulated and the measured temperature increase was within a &plusmn;10&percnt; margin relative to the simulation. The global SAR power limit per channel was found to be higher (i.e. more allowed power) than the worst case local SAR power limit, and thus did not impose additional power penalty. The resolution achieved was 0.6 mm isotropic for the 3D protocol and 0.6 by 0.6 by 2.5 mm for the 2D protocol. The average SNR was measured within the vessel wall location of the two carotid arteries and found to be 27&plusmn;6 for the DANTE images and for the static tissue closer to the skin the SNR was 55&plusmn;2. In conclusion, a 4Tx/4Rx coil was designed to target the carotid arteries operating under pTx mode and a black blood imaging sequence was implemented for blood signal suppression and vessel wall imaging. The initial results from the subject and phantom imaging show satisfactory blood suppression and spatial resolution.

<p>Намера студије јесте да се целокупни досадашњи драмски опус Виде Огњеновић<br />сагледа у ширем контексту савремене српске драматургије и књижевне традиције. Овакав<br />задатак подразумева анализу примењеног литерарно-драматуршког поступка, тематско-<br />мотивских одредница, жанровских и стилских особености, језичког израза,<br />карактеризације ликова, односа према историјским, политичким, идеолошким, културним,<br />социјалним и другим друштвеним феноменима. За реализацију тако дефинисаног циља<br />истраживања, било је неопходно формирати својеврсни координатни систем. Унутар<br />система једна оса представља најзначајније ауторе и њихова репрезентативна дела, који су<br />кључни за развој савремене српске драме од Другог светског рата до прве деценије овог<br />века, а друга оса означава књижевну традицију као недвосмислену исходишну тачку и<br />креативну инспирацију. Рад је подељен у три органски повезане целине: &bdquo;Савремена<br />српска драма&rdquo;, &bdquo;Драмски опус Виде Огњеновић&rdquo; и &bdquo;Књижевна традиција као креативна<br />инспирација</p> / <p>Namera studije jeste da se celokupni dosadašnji dramski opus Vide Ognjenović<br />sagleda u širem kontekstu savremene srpske dramaturgije i književne tradicije. Ovakav<br />zadatak podrazumeva analizu primenjenog literarno-dramaturškog postupka, tematsko-<br />motivskih odrednica, žanrovskih i stilskih osobenosti, jezičkog izraza,<br />karakterizacije likova, odnosa prema istorijskim, političkim, ideološkim, kulturnim,<br />socijalnim i drugim društvenim fenomenima. Za realizaciju tako definisanog cilja<br />istraživanja, bilo je neophodno formirati svojevrsni koordinatni sistem. Unutar<br />sistema jedna osa predstavlja najznačajnije autore i njihova reprezentativna dela, koji su<br />ključni za razvoj savremene srpske drame od Drugog svetskog rata do prve decenije ovog<br />veka, a druga osa označava književnu tradiciju kao nedvosmislenu ishodišnu tačku i<br />kreativnu inspiraciju. Rad je podeljen u tri organski povezane celine: &bdquo;Savremena<br />srpska drama&rdquo;, &bdquo;Dramski opus Vide Ognjenović&rdquo; i &bdquo;Književna tradicija kao kreativna<br />inspiracija</p> / <p>This study is aimed at offering an overview of the entire dramatic oeuvre of Vida<br />Ognjenović to date within the wider context of the contemporary Serbian dramaturgy and literary<br />tradition. This objective entails an analysis of the literary-dramatic procedure used, as well as the<br />thematic-motif determinants, distinctive features in regard to genre and style, linguistic<br />expression, characterisation, attitude towards historical, political, ideological, cultural, social and<br />other societal phenomena. In order to accomplish the objective of research thus formulated, it<br />was necessary to form a singular coordinate system. One coordinate axis represents major<br />authors and their representative works, which bear crucial significance for the development of<br />the contemporary Serbian drama from World War II to the first decade of this century, while the<br />other axis represents literary tradition as an unambiguous point of origin and creative inspiration.<br />The study is divided into three organically related units: &lsquo;Contemporary Serbian drama&rsquo;,<br />&lsquo;Dramatic oeuvre of Vida Ognjenović&rsquo; and &lsquo;Literary tradition as creative inspiration&rsquo;.</p>

Les mémoires à changement de phase (PRAM) développées par l’industrie de la microélectronique utilisent la capacité d’un materiau chalcogénure à passer rapidement et de façon réversible d’une phase amorphe à une phase cristalline. Le passage de la phase amorphe à la phase cristalline s’accompagne d’un changement de la résistance électrique du matériau. La transition amorphe vers cristallin est obtenue par un chauffage qui porte la cellule mémoires au delà de la température de transition du verre. Le verre ternaire de chalcogène Ge2Sb2Te5 (GST-225) est probablement le matériau amené à être le plus utilisé dans la prochaine génération de dispositifs de stockage de masse. La thermoréflectométrie résolue en temps (TDTR) et la radiométrie photothermique modulée (MPTR) sont utilisées ici pour étudier les propriétés thermiques des constituants des PRAM déposés sous forme de couche mince sur des substrats de silicium. Les diffusivités thermiques et les résistances thermiques de contact des films PRAM sont estimées. Ces paramètres sont identifiés en utilisant un modèle d’étude des transferts de chaleur basé sur la loi de Fourier et utilisant le formalisme des impédances thermiques. Ces mesures ont été effectuées pour des températures allant de 25 à 400°C. Les modifications de structure et de compositions chimiques causées par les hautes températures au cours des expériences sont aussi étudiées via des analyses par les techniques de DRX, MEB, TOF-SIMS et ellipsométrie.Les propriétés thermiques des GST - 225, isolants, électrodes de chauffage et électrodes métalliques mise en œuvre dans ce type de dispositif de stockage sont ainsi mesuré a l’échelle submicrométrique. / The Phase change Random Access Memories (PRAM), developed by semiconductor industry are based on rapid and reversible change from amorphous to crystalline stable phase of chalcogenide materials. The switching between the amorphous and the crystalline phase leads to change of the electrical resistance of material. The amorphous-to-crystalline transition is performed by heating the memory cell above the glass transition temperature (~130°C). The chalcogenide ternary compound glass Ge2Sb2Te5 (GST-225) is probably the candidate to become the most exploited material in the next generation of mass storage architectures. The Time Domain ThermoReflectance (TDTR) and the Modulated PhotoThermal Radiometry (MPTR) have been implemented to study the thermal properties of constituting element of PRAM deposited as thin layer (~100 nm) on silicon substrate. The thermal diffusivity and the Thermal Boundary Resistance of the PRAM film are retrieved. These parameters are identified using a model of heat transfer based on Fourier’s Law and the thermal impedance formalism. The measurements were performed in function of temperature from 25°C to 400°C. Structural and chemical changes due to the high temperature during the experimentation have been also investigated by using XRD, SEM, TOF-SIMS and ellipsometry techniques. The thermal properties of GST-225, insulator, heating and metallic electrode involved in these kind of storage devices were thus measured at a sub micrometric scale.

Die additiven Fertigungstechnologien erleben seit einigen Jahren einen enormen Zuspruch bei der Herstellung von Einzelteilserien mit komplexen, endkonturnahen Geometrien und der Verarbeitung von Sonder- oder hybriden Werkstoffen. Prinzipiell lassen sich die Verfahren gemäß VDI- Richtlinie 3404 in drahtbasierte und pulverbasierte unterteilen. Eine weitere Unterteilung erfolgt hinsichtlich der Ausschmelztechnologie. Allen Verfahren ist gleich, dass schichtweise der Grundwerkstoff an den Stellen aufgetragen wird, wo er gemäß Endkontur benötigt wird. Damit ist ein immer wiederkehrender Wärmeeintrag verbunden, der somit Einfluss auf die Mikrostruktur der Bauteile und gleichzeitig auch auf die mechanischen Endeigenschaften ausübt. Die so erzeugten Komponenten sollten wenig Verzug oder Eigenspannungen als auch keine Porosität aufweisen, um die Gebrauchseigenschaften nicht negativ zu beeinflussen. Das Ziel ist es mittlerweile, diese verschiedenen Technologien numerisch abzubilden, um die Bauteileigenschaften vorherzusagen und ggf. Optimierungspotenziale zu eruieren. Der untersuchte Prozess ist das drahtbasierte Mehrlagenschweißen mittels des Metallschutzgasschweißens, bei dem neben der Simulation auch die Validierung im Fokus hinsichtlich Geometrie und Gefügeausbildung in den Schweißlagen stand. Diesbezüglich wurden im vorliegenden Fall zum einen alle, für die numerische Simulation notwendigen Materialparameter (mechanische und thermophysikalische Kenngrößen) des Schweißzusatzwerkstoffes G4Si1 bestimmt und in ein kommerzielles FEM-Programm (MSC Marc Mentat) implementiert. Zum anderen erfolgt zukünftig die wissenschaftliche Analyse der Verbesserung der Bauteileigenschaft, in dem die Schweißnaht unter Ausnutzung der Schweißhitze warmumgeformt wird. Erste Ergebnisse numerischer Simulationsergebnisse zeigen positive Effekte. Diese zeigen mikrostrukturelle Veränderungen (Kornfeinung durch Rekristallisation) und führten letztendlich zur Steigerung der mechanischen Eigenschaften. Der Vorteil dieser Verfahrenskombination ist außerdem die Kompensation des Verzuges durch die gezielte Umformung und einem gleichzeitigen „Richten“.