Various solar energy technologies are being developed to harness the available environmentally friendly and sustainable solar radiation. New ways of utilizing this "free" power for different energy consuming processes continue to be created. In this thesis, a multi-stage solar energy concentrating system has been developed and its feasibility as a radiation source for polymer processing has been explored. The solar energy concentrator (SEC) facility comprises a modified Cassegrainian configuration combined with auxiliary imaging and non-imaging optics, serving as an alternative energy source for polymer joining, ageing and adhesive curing. Modeling and improvement of various aspects of the operation and performance of the SEC facility have been implemented. Optical ray tracing models of the Cassegrainian concentrator with various conventional imaging components and nonimaging concentrators have been created to optimize the optical layout and system efficiency. On their basis, combined 3D ray tracing computer models integrated with the mechanical components have been developed to simulate the entire SEC facility and predict the image size, location and orientation. Additionally, the energy transfer, radiation absorption and heat generation and transfer in the irradiated polymer have been modeled in order to study the radiation-polymer interaction. One novel contribution of this research is the enhancement of the image forming concentrator with non-imaging cone-like concentrators (conical and compound parabolic concentrator (CPC)), utilizing their inherent disadvantage of excessive length. Compared to the refractive type means of transmitting concentrated solar radiation, the truncated cone and CPC concentrators have been found more efficient enhancing further the concentration and widening the utilized spectral range. The experimental studies have demonstrated that transparent and colored, similar and dissimilar polymers can be successfully joined using the SEC facility. The especially developed through-transmission technique removes the need to use a special absorbing medium of the radiant energy required by current advanced welding techniques. The tensile strengths of the joints achieved are comparable to those achieved for similar polymers with other advanced plastic joining methods. The results from the polymer ageing experiments have shown that ultraaccelerated exposure to concentrated sunlight can be performed with the SEC facility without introducing spurious failure mechanisms. Based on the preliminary investigation on adhesive curing utilizing concentrated solar radiation, it has been concluded that with carefully chosen light-curing adhesives solar radiation can be a useful radiation source for adhesive curing.

Friction joining techniques, such as Friction Stir Spot Welding (FSSW) and high power Ultrasonic Welding (USW), could offer a solution for joining dissimilar materials combinations, such as aluminium (Al) to magnesium (Mg), where high intermetallic reaction rates make the use of conventional joining techniques problematic. Ultrasonic welds have been produced between 1 mm gauge Al 6111-T4 and Mg AZ31-H24 sheets, and the interfacial reaction has been studied as a function of welding time. For this welding system, the mechanical properties of the joints were optimised when a double reed welding system was employed to join materials that had been prepared using 800 grit SiC paper under a clamping force of 1.9 kN, and when the materials were oriented with the rolling direction parallel to the vibration direction. Welds produced between Al and Mg achieved similar peak lap shear strengths to those produced between Mg and Mg at welding times of 0.4 s, but the failure energy of the Al-Mg welds was less than half that of the parent material. In addition, the Al-Mg welds always failed at the interface between the sheets, rather than the desirable, and more energy intensive, pullout mechanism. The inferior mechanical properties were attributed to the rapid formation of a brittle intermetallic layer that initially formed as islands of the γ-Al12Mg17 phase. These islands rapidly spread and became continuous within 0.3 s of welding time, at which point a second sublayer of the β-Al3Mg2 phase began to form on the Al side of the intermetallic reaction layer. The combined layers reached a total thickness of 20 µm within 0.9 s of welding time, with the β-Al3Mg2 sublayer becoming the thicker of the two by this point. At longer welding times, interface liquation was observed at temperatures below the recognised lowest temperature eutectic reaction in the Al-Mg binary phase diagram. This was the result of the alloying elements present in the system and there was no depression in the melting point as a result of the high strain rate associated with this process, as has been proposed elsewhere. The rate of growth of the intermetallic layer during welding was higher than in static heat treatments, which was most likely due to the deformation causing microcracking in the brittle intermetallic layer, allowing short circuit diffusion to occur, and enhancing the growth rate by a factor of approximately 2. Finally, attempts were made to limit the rate of intermetallic compound (IMC) formation by applying coatings to the Mg sheet. The effect of the coatings was to reduce the overall IMC layer thickness by 50 %.

No description available.

The following report conducted by the theoretical research and experimental study in the University of Halmstad. The focus of the project is experimental investigation on weld characteristics for shield metal arc welding with SS304 & SS409. Welding is a joining process of similar metals but nowadays it is also joined dissimilar metals by the application of heat. The different types of welding process are available in industry. Welding can be done with or without the application of pressure and filler materials in shielded metal arc welding (SMAW), an arc between a covered electrode and a weld pool is used to accomplish a weld. As the welder steadily feeds the covered electrode into the weld pool, the decomposition of the covering evolves into gases that shield the pool. Austenitic stainless steel and Martensitic chrome alloys is widely used materials in the current industrial area including higher and lower temperature applications such as storage tanks, pressure cups, furnace equipment’s etc. This paper concentrated to the investigate the dissimilar material joining by using shield metal arc welding and study the welding characteristics and do the mechanical tests. The aim of this study performance of steel and maximum hardness of welded material, microstructure of steel on next phase of project. The results will be used to character of dissimilar material performance.

Indiana University-Purdue University Indianapolis (IUPUI) / DNA double strand breaks (DSB), particularly those induced by ionizing radiation (IR) are complex lesions and if not repaired, these breaks can lead to genomic instability, chromosomal abnormalities and cell death. IR-induced DSB often have DNA termini modifications including thymine glycols, ring fragmentation, 3' phosphoglycolates, 5' hydroxyl groups and abasic sites. Non-homologous end joining (NHEJ) is a major pathway responsible for the repair of these complex breaks. Proteins involved in NHEJ include the Ku 70/80 heterodimer, DNA-PKcs, processing proteins including Artemis and DNA polymerases µ and λ, XRCC4, DNA ligase IV and XLF. The precise molecular mechanism of DNA-PK activation and Artemis processing at the site of a DNA DSB has yet to be elucidated. We have investigated the effect of DNA sequence and structure on DNA-PK activation and results suggest a model where the 3' strand of a DNA terminus is responsible for annealing and the 5' strand is involved in activation of DNA-PK. These results demonstrate the influence of DNA structure and orientation on DNA-PK activation and provide a molecular mechanism of activation resulting from compatible termini, an essential step in microhomology-mediated NHEJ. Artemis, a nuclease implicated in processing of DNA termini at a DSB during NHEJ, has been demonstrated to have both DNA-PK independent 5'-3' exonuclease activities and DNA-PK dependent endonuclease activity. Evidence suggests that either the enzyme contains two different active sites for each of these distinct processing activities, or the exonuclease activity is not intrinsic to the Artemis polypeptide. To distinguish between these possibilities, we sought to determine if it was possible to biochemically separate Artemis endonuclease activity from exonuclease activity. An exonuclease-free fraction of Artemis was obtained that retained DNA-PK dependent endonuclease activity, was phosphorylated by DNA-PK and reacted with an Artemis specific antibody. These data demonstrate that the exonuclease activity thought to be intrinsic to Artemis can be biochemically separated from the Artemis endonuclease. These results reveal novel mechanisms of two critical NHEJ proteins, and further enhance our understanding of DNA-PK and Artemis activity and their role in NHEJ.

Flugzeuge sind üblicherweise als Rahmenstrukturen aus Leichtbauwerkstoffen wie faserverstärktem Kunststoff, Titan- oder Aluminiumlegierungen gestaltet. Je nach Anwendungsfall reicht die Tragfähigkeit der eingesetzten Streben von wenigen Kilonewton bis zu mehr als 250 kN. Die Verbindungen der Streben mit Anschlussstücken sind häufig komplex, sodass hohe Kosten für die montierten Bauteile entstehen. Fügen durch elektromagnetische Kompression (EMK) stellt aufgrund der verfahrensspezifischen Vorteile eine vielversprechende Alternative dar, um Verbindungen deutlich einfacher zu realisieren, insbesondere wenn Streben aus Aluminiumrohr eingesetzt werden.

Aircraft are typically designed as frame structures using lightweight materials such as fiber reinforced plastics, titanium or aluminum alloys. Depending on the application, the load capacity of the struts used ranges from a few kilonewtons to more than 250 kN. The connections between the struts and the connectors are often complex, resulting in high costs for the assembled components. Joining by electromagnetic forming (EMF) offers a promising alternative to make connections much simpler, especially when aluminum tube struts are used.

No description available.

<p> Repair of double-strand breaks is critical for the preservation of genomic integrity and cellular viability. A predominant pathway implicated in the repair of such lesions is the evolutionarily conserved non-homologous end-joining (NHEJ) pathway. Among the major constituents of this pathway in Saccharomyces cerevisiae is Nej1, for which a clear biochemical function has not been determined. The results presented in this work demonstrate that Nej1 exhibits a DNA binding activity comparable to Lif1, with an apparent dissociation constant of 1.8 μM. Characterization of the DNA binding activity revealed that although short ~20 bp substrates can suffice, binding is enhanced with longer substrates (>300). This DNA binding activity supports the hypothesis that Nej1 plays a direct role in the repair of DNA double-strand breaks. Structure-function studies indicated that the C-terminus of Nej1 is not only required, but is sufficient, for mediating DNA interactions. Structural characterization revealed that Nej1 exists as a dimer, and that residues 1-244 are sufficient for dimer formation. Examining the ability of this truncated Nej1 (aa 1-244) to perform NHEJ, revealed a defect in end-joining as measured by an in vivo plasmid repair assay. Preliminary functional and structural studies on the Nej1-Lif1 complex suggest that the proteins stably co-purify and the complex binds DNA with a higher affinity than each independent component. The significance of these results is discussed with reference to current literature on Nej1 and other end-joining factors (mammalian and yeast), specifically the recently identified putative mammalian homologue of Nej1, XLF. Collectively, these results demonstrate that although there are several functional similarities, there also appear to be important differences in the structure-function relationships of Nej1 and XLF, and Nej1/XLF and Lif1/Xrcc4.</p> / Thesis / Master of Science (MSc)

Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties.   This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis.  Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature. / <p>QC 20170519</p>