M.A. / Even at a superficial glance there seems to be remarkable similarities between the "Border trilogy" of the American author Cormac McCarthy and the work of the Afrikaans author Alexander Strachan. The last three novels by McCarthy, All the Pretty Horses (1992), The Crossing (1994) and Cities of the Plain (1999), are referred to as the "Border trilogy". The first three novels by Strachan are also sometimes referred to as a "trilogy". Frontiers/borders are important in the novels under discussion: The Crossing (1994), Die jakkalsjagter (1990) and Die werfbobbejaan (1994). The Crossing is the second novel of the 'Border trilogy". The title of Strachan's fist work is 'n Wereld sonder grense ("A world without borders"). In The Crossing tracking a wolf plays an important role while Die jakkalsjagter is about hunting a jackal. Die werfbobbejaan is about hunting down a baboon. Both McCarthy's and Strachan's works have been compared to the Western (films/novels dealing with the cowboys of North America). These superficial similarities seem to invite further comparison. The following themes are present in both authors' works and are compared in this study: The world can never be known The world is incomprehensible. It is constantly changing and always out of reach. The world is like "a snowflake" and like "breath" and cannot be held, because it only exists in people's hearts. The world is also incomprehensible in Strachan's work, because all certainties are undermined. Khera cannot understand Zuhiland in the same "logical" way that she could understand her world in Cape Town. The strange stories told by the people in Zululand (izinganekwane) make her aware of supernatural powers. Nothing can really be known about the world. The story that the witness tells becomes the world All objects are without meaning unless their stories are known. Truth is only to be found in narration. The world exists in narration. Therefore "the witness is all". Free will and predetermination The view of the world and our destiny in the world in The Crossing is compared with the view of the world in Die jakkalsjagter and Die werfbobbejaan. There is not one final answer to the question of determinism and free will in The Crossing. On the one hand it seems that history happens according to a predetermined plan of God. On the other hand it seems that human beings can make decisions and be in control. In this novel we find the idea that the future and the past can only be known as it exists in the present. The Strachan novels, Die jakkalsjagter en Die werfbobbejaan, reflect a certain determinism. Everything heads towards a final showdown with the death of the old man in the sod house. Khera's actions are predetermined. Things happen without her intention. The importance of stories is found in all three novels under discussion, The Crossing, Die jakkalsjagter and Die werfbobbejaan. "Things separate from their stories have no meaning. They are only shapes. Of a certain size and color. A certain weight. When their meaning has become lost to us they no longer have even a name. The story on the other hand can never be lost from its place in the world for it is that place" (Crossing: 142-143). The importance of the story is that it gives meaning to the things. All stories are the same story. The izinganekwane could be parallelled to the corrido (Spanish tales). Both are part of a hostile country, a different language and both are old tales that seem to determine the future.

PFEIFER František: Production of support by solid forming. A Graduation Thesis of Master´s Studies, the 5th Year of Study, the School-year 2008/2009, FSI VUT Brno, Department of Machining, May 2009, Pages No. 94, Pictures No. 37, Tables No. 3, Appendixes No. 13. The Graduation Thesis, elaborated in the framework of engineering studies, presents the production technology of support component from steel ČSN 12 010. A material is a rod of the 130 – 251 ČSN 42 5510. A yearly production is 95 000 pieces. Based on the studies of possible production technologies was proposed the technology of production by the vertical forging press LMZ 6500B (Šmeral Brno a. s.) with a nominal forming power of 65 MN, flash and pellicle trimming on a trimming press with a nominal power of 8 MN. For this option, the required technological calculations, the design of the die, the specification of production machines and a simulation forming process which is made in the software QFORM have been carried out.

Thread rolling is a unique metal forming process which is commonly used to form screw threads on threaded fasteners and precision leadscrews at relatively high rates of speed. Threads are formed on a cylindrical blank by flat or cylindrical dies having the reverse form on them, which rotate and penetrate the blank simultaneously, to plastically deform it into a precise geometry. Thread rolling dies are exposed to a complex state of cyclical contact stresses that eventually cause the dies to fail by fatigue and wear. The stress state is not easily ascertained through standard analytical models due to complex geometry and process conditions. This research seeks to better understand the state of contact stresses present in cylindrical thread rolling dies as they form material, to aid in identifying and testing economical methods of improving thread rolling die fatigue life. Some work has been published on using FEA simulation software to model the thread rolling process, but no work has been published on using FEA software to analyze the stresses in thread rolling dies. DEFORM®-3D Forming Simulation Software by Scientific Forming Technologies Corporation in Columbus, Ohio was used to simulate the throughfeed thread rolling process and model the state of stresses in the dies. The results were compared to the Hertzian contact stress model and the Smith Liu equations for rolling and sliding friction. Fatigue life prediction methods involving S-N curves, surface fatigue strength, and Weibull probability distributions were tested using the simulation data against field results. An optimized die design was generated from a design of experiments simulating different die design geometry. Findings show that field failures correlate well to the DEFORM® simulation results. The Hertz model with Smith Liu equations improved correlation with the simulation. Fatigue life prediction models correlated reasonably well to field results using the simulation data for inputs. These findings can aid in selecting appropriate die materials, design parameters, and fatigue life treatments.

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As the first level interconnection in electronic packages, chip attachment plays a key role in the total packaging process. Sintered nanosilver paste may be used as a lead-free alternative to solder for die-attachment at sintering temperature below 300 °C without applying any pressure. Typically, the substrate, such as direct bond copper (DBC) substrates, has surface metallization such as silver or gold to protect the copper surface from oxidation during the sintering process. This study focused on developing techniques for die-attachment on pure copper surface by low-temperature sintering of nanosilver paste. One of the difficulties lies in the need for oxygen to burn off the organics in the paste during sintering. However, the copper surface would oxidize, preventing the formation of a strong bond between sintered silver and copper substrate. Two approaches were investigated to develop a feasible technique for attachment. The first approach was to reduce air pressure as a means of varying the oxygen partial pressure and the second approach was to introduce inert gas to control the sintering atmosphere. For the first method, die-shear tests showed that increasing the oxygen partial pressure (PO₂ from 0.04 atm to 0.14 atm caused the bonding strength to increase but eventually decline at higher partial pressure. Scanning electron microscopy (SEM) imaging and energy dispersive spectroscopy (EDS) analysis showed that there was insufficient oxygen for complete organics burnout at low PO₂ condition, while the copper surface was heavily oxidized at high PO₂ levels, thus preventing strong bonding. A maximum bonding strength of about average 8 MPa was attained at about PO₂ = 0.08 atm. With the second method, the die-shear strength showed a significant increase to about 24 MPa by adjusting the oxygen exposure temperature and time during sintering. The processing conditions necessary for bonding large-area chips (6 mm à 6 mm) directly on pure copper surface by sintering nanosilver paste was also investigated. A double-print process with an applied sintering pressure of less than 5 MPa was developed. Die-shear test of the attached chips showed an average bonding strength of over 40 MPa at applied pressure of 3 MPa and over 77 MPa under 12 MPa sintering pressure. SEM imaging of the failure surface showed a much denser microstructure of sintered silver layer when pressure was applied. X-ray imaging showed a bond layer almost free of voids. Because the samples were sintered in air, the DBC surface showed some oxidation. Wirebondability test of the oxidized surface was performed with 250 μm-diameter aluminum wires wedge-bonded at different locations on the oxidized surface. Pull test results of the bonded wires showed a minimum pull-strength of 400 gram-force, exceeding the minimum of 100-gf required by the IPC-TM-650 test standard. / Master of Science

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Solarzellen auf Basis von hybriden Perowskiten, wie zum Beispiel Methylammoniumbleitriiodid (CH3NH3PbI3), stellen eine der vielversprechendsten Solarzellenkonzepte dar. Dabei wurden Wirkungsgrade über 20 % gezeigt. Perowskite werden durch verschiedene lösungsbasierte Techniken abgeschieden. Daher konzentriert sich der erste Teil dieser Dissertation auf die Bildung von hybriden Perowskiten in der Lösung, während der zweite Teil der Stabilität von hybriden Perowskiten gewidmet ist. Im ersten Teil, wird die Bildung von Polyiodidplumbaten aus PbI2 in Lösung nachgewiesen. Die Bildung dieser Polyiodidplumbate konnte unabhängig von dem gewählten Lösungsmittel sowie unabhängig von der Beigabe von Methylammoniumiodid (CH3NH3I) beobachtet werden. Die Polyiodidplumbate zeigten, ähnlich wie CH3NH3PbI3, ein Photolumineszenzmaximum bei einer Wellenlänge von 760 nm, was auf einen gemeinsamen Ursprung des angeregten Zustands in PbI2-Komplexen und CH3NH3PbI3 hindeutet. Im zweiten Teil wurden darüber hinaus die Lichtbeständigkeit sowie die thermische und kompositionelle Stabilität untersucht. Die Untersuchung der thermischen Stabilität hat gezeigt, dass Tempern bei T <190 °C zu einer Verbesserung der Morphologie und der optoelektronischen Eigenschaften führt. Oberhalb einer Temperatur von 190 °C kam es dabei zur Zersetzung des Materials. Die Stabilität der Komposition wurde anhand von CsPb(I[1-x]Br[x])3-Perowskiten untersucht. Die Herstellung von Perowskiten mit einer großen Bandlücke war zunächst nicht möglich, da es bei den dafür notwendigen Kompositionen (0,3<x<1) zur Phasentrennung kommt. Im Gegensatz dazu konnte durch den Zusatz von Ethylendiammoniumdiodid (EDDI) zu CH3NH3PbI3 die Bandlücke zwischen 1,6 und 1,8 eV variiert werden. Die Lichtstabilität von CH3NH3PbI3, CH(NH2)2PbI3 sowie gemischt Perowskiten wurde mittels in-situ Infrarotspektroskopie analysiert. Die Zersetzung des Materials war durch die lichtinduzierte Spaltung der N-H-Bindungen bei hv ≥ 2,72 eV gekennzeichnet. / Hybrid perovskites such as methylammonium lead iodide, CH3NH3PbI3, are one of the most promising absorber materials for photovoltaic energy conversion with demonstrated power conversion efficiencies beyond 20 %. In addition, hybrid perovskites can be deposited by various solution-based fabrication techniques. Therefore, the first part of this dissertation is focused on the formation of hybrid perovskites in the precursor solution, while the second part is dedicated to the study of the stability of hybrid perovskites. In the first part of this thesis, the formation of polyiodide plumbates between molecules of PbI2 was detected. Importantly, the formation of polyiodide plumbates was observed independently of the solvent choice or the presence of CH3NH3I. The polyiodide plumbates exhibited a photoluminescence peak located at 760 nm, similarly to CH3NH3PbI3, which suggests a common origin of the excited state in PbI2 complexes and CH3NH3PbI3. In the second part of this thesis, the thermal, compositional, and photostability of perovskite thin films were evaluated. The study of the thermal stability has shown that post-annealing at T < 190 °C leads to the improvement of morphology and optoelectronic properties. Above 190 °C, CH3NH3PbI3 was found to degrade. Next, the compositional stability of mixed CsPb(I[1-x]Br[x])3 perovskites was investigated. A fundamental miscibility gap between 0.3 < x <1 was demonstrated, that impedes the preparation of high band-gap perovskites. To overcome this intrinsic instability, a new approach for band-gap engineering was developed. An addition of ethylenediammonium diiodide (EDDI) allowed to alter the band gap of CH3NH3PbI3 from 1.6 to 1.8 eV. Finally, the influence of light on the stability of hybrid perovskites was studied. A degradation of CH3NH3PbI3, CH(NH2)2PbI3, as well as mixed perovskites, was observed through photo-dissociation of N-H bonds with hν ≥ 2.72 eV by means of in-situ Fourier-transform infrared spectroscopy.