There are numerous experiments for the exploration of the corium spreading behaviour, but comparable data have not been available up to now in the field of the long term behaviour of a corium expanded in a core catcher. The difficulty consists in the experimental simulation of the decay heat that can be neglected for the short-run course of events like relocation and spreading, which must, however, be considered during investigation of the long time behaviour. Therefore the German GRS, defined together with Battelle Ingenieurtechnik a benchmark problem in order to determine particular problems and differences of CFD codes simulating an expanded corium and from this, requirements for a reasonable measurement of experiments, that will be performed later. First the finite-volume-codes Comet 1.023, CFX 4.2 and CFX-TASCflow were used. To be able to make comparisons to a finite-element-code, now calculations are performed at the Institute of Safety Research at the Forschungszentrum Rossendorf with the code ANSYS/FLOTRAN.For the benchmark calculations of stage 1 a pure and liquid melt with internal heat sources was assumed uniformly distributed over the area of the planned core catcher of a EPR plant. Using the Standard-k-e-turbulence model and assuming an initial state of a motionless superheated melt several large convection rolls will establish within the melt pool. The temperatures at the surface do not sink to a solidification level due to the enhanced convection heat transfer. The temperature gradients at the surface are relatively flat while there are steep gradients at the ground where the no slip condition is applied. But even at the ground no solidification temperatures are observed. Although the problem in the ANSYS-calculations is handled two-dimensional and not three-dimensional like in the finite-volume-codes, there are no fundamental deviations to the results of the other codes.

Since materials properties are determined by the interactions between the constituent atoms, an accurate description of the inter-atomic interactions is crucial to characterize and control material properties. Particularly, a quantitative understanding of the formation and nature of defects and impurities becomes increasingly important in the era of nanotechnology, as the imperfections largely influence many properties of nanoscale materials. Indeed, due to its technological importance and scientific interest, there have been significant efforts to better understand their behavior in semiconductors and oxides, and their interfaces, yet many fundamental aspects are still ambiguous due largely to the difficulty of direct characterization. Hence, our study has focused on developing a better understanding of atomic-scale defects and impurities using first principles quantum mechanical calculations. In addition, based on the improved understanding, we have attempted to address some engineering problems encountered in the current technology. The first part of this thesis focuses on mechanisms underlying the transient enhanced diffusion of arsenic (As) during post-implantation annealing by examining the interaction of As with vacancies in silicon. In the second part, we address some fundamental features related to plasma-assisted nitridation of silicon dioxide; this study shows that oxygen vacancy related defects play an important role in (experimentally observed) peculiar nitridation at the Si/SiO2 interface during post O2 annealing. In the third part, we examine the interaction between vacancies and dopants in sp2–bonded carbon such as graphene and nanotube, specifically the formation and dynamics of boron-vacancy complexes and their influence on the electrical properties of host materials. In the fourth part, we study the interfacial interaction between amorphous silica (a-SiO2) and graphene in the presence of surface defects in a-SiO2; this study shows possible modifications in the electronic structure of graphene upon the surface defect assisted chemical binding onto the a-SiO2 surface. In the last part, we examine the structural and electronic properties of bismuth vanadate (BiVO4) which is a promising photocatalyst for water splitting to produce hydrogen; this study successfully explains the underlying mechanism of the interesting photocatalytic performance of BiVO4 that has been experimentally found to strongly depend on structural phase and doping. / text

In the design of digital signal processing systems, where single-precision results are required, the power dissipation and area of parallel multipliers can be significantly reduced by truncating the less significant columns and compensating to produce an approximate rounded product. This dissertation presents the design of truncated multiplications of signed inputs utilizing a new number system, the negative fractional two's complement number system which solves an inherent problem of the conventional two's complement number system. This research also presents a new truncated multiplication method to reduce the errors with only slightly more hardware. Error, area, delay and dynamic power estimates are performed at the structural HDL level. The new method is also applied to various conventional number systems. For division, which is the slowest and most complex of the arithmetic operations, a new truncated division method is described that yields the same errors as those of true rounding without additional execution time that is normally required for true rounding. The new method is also applied to various conventional number systems.

Dieses Manuskript entstand aus Vorlesungen über Geodätische Berechnungen an der Hochschule für Technik und Wirtschaft Dresden. Da diese Lehrveranstaltung im ersten oder zweiten Semester stattfindet, werden noch keine Methoden der höheren Mathematik benutzt. Das Themenspektrum beschränkt sich deshalb weitgehend auf elementare Berechnungen in der Ebene. Nur im Kapitel 7 kommen einige Methoden der Vektorrechnung zum Einsatz.

This is a Masters Thesis report of a project carried out at Scania AB in Södertälje. The project concerns rationalizing Chassis calculations for use in truck Frame design. The subject for analysis is a six-wheeled articulated truck, and the load cases under study is Lateral Loading, Frame Torsion and Vertical Load on Kingpin. Making robust deformation and stress models with a calculation time sufficiently short and accuracy consistently high for efficient design work is an arduous task. This report presents several approaches to tackle this type of problem. By means of simplifying contemporary modeling approaches and methods and automating the setup process, a method that enables short calculation iterations on a chassis frame of a truck is achieved. This is done using the Catia GAS framework in conjunction with several other licences commonly used by designers.

The Oak Ridge Isotope Generation and Depletion – Automatic Rapid Proccessing (ORIGEN-ARP) deterministic code has been extensively utilized for determining nuclide concentrations at various specific burnup values for a variety of nuclear reactor designs. Given nuclide concentrations or ratios, such calculations can be used in nuclear forensics and nuclear non-proliferation applications to reverse-calculate the type of reactor and specific burnup of the fuel from which the nuclides originated. Recently, Los Alamos National Laboratory has released a version of its probabilistic radiation transport code, MCNPX 2.6.0, which incorporates a fuel burnup feature which can also determine, via the probabilistic Monte Carlo method, nuclide concentrations as a function of fuel burnup. This dissertation compares the concentrations of 46 nuclides significant to nuclear forensics analyses for different reactor types using results from the ORIGEN-ARP and the MCNPX 2.6.0 codes. Three reactor types were chosen: the Westinghouse 17x17 Pressurized Water Reactor (PWR), the GE 8x8-4 Boiling Water Reactor (BWR), and the Canadian Deuterium Uranium, CANDU-37, reactor. Additionally, a sensitivity study of the different reactor parameters within the MCNPX Westinghouse 17x17 PWR model was performed. This study analyzed the different nuclide concentrations resulting from minor perturbations of the following parameters: assembly rod pitch, initial moderator boron concentration, fuel pin cladding thickness, moderator density, and fuel temperature. / text

La tesi estudia l'acoblament magnètic en sistemes de diferent dimensionalitat amb mètodes multireferencials. L’objectiu principal del treball és calcular propietats macroscòpiques, com la dependència de la susceptibilitat magnètica amb la temperatura, a partir de la constant d'intercanvi magnètic calculada, J. Aquest paràmetre microscòpic quantifica la interacció magnètica entre dos centres i es pot extreure per ajust de la corba de susceptibilitat experimental en sistemes finits però això no és possible en sistemes magnètics infinits com cadenes o capes 2D. L’estratègia del treball és calcular J en petits clusters i simular els sistemes estesos utilitzant aquesta J en l’Hamiltonià de Heisenberg en models de 8 a 16 centres. Amb l’espectre obtingut es construeixen les corbes de dependència tèrmica de la susceptibilitat magnètica que, comparades amb les experimentals, donen la possibilitat de quantificar les interaccions magnètiques dels materials estudiats a nivell microscòpic. S'han estudiat diferents tipus de sistemes estesos com cadenes i xarxes hexagonals, on els centres magnètics són ions de metalls de transició. / The thesis studies the magnetic coupling in systems of different dimensionality, by using multireference methods. The aim of the work is to determine macroscopic properties such as the thermal dependency of magnetic susceptibility, from the calculated magnetic exchange constant J. This microscopic parameter quantifies the magnetic interaction between two magnetic sites and can be extracted from the experimental susceptibility curve in finite systems. However this extraction is not possible in extended magnetic systems such as chains or 2D-layers. The strategy followed consists in calculating J in small clusters and in simulating the extended systems by introducing the calculated J in the Heisenberg Hamiltonian of 8 to 16 site models. From the spectrum, the thermal dependency of the magnetic susceptibility is the calculated. When compared to the experimental one, this curve gives a quantification of the magnetic interactions of the studied materials at the microscopic level. We have studied different types of extended systems such as chains and hexagonal lattices, where the magnetic sites are transition metal ions.

Aquest treball presenta l’estudi teòric de l’anisotropia magnètica en complexos de metalls de transició, combinant esquemes de càlcul multiconfiguracionals relativistes amb derivacions analítiques basades en la teoria del camp del lligand, el que permet racionalitzar a través de conceptes senzills els resultats quantitatius obtinguts i interpretar les propietats estudiades. Es desenvolupa primer una metodologia per extreure els paràmetres d’anisotropia en complexos mononuclears de metalls de transició. El mètode es basa en assignar els resultats d’un càlcul ab initio d’alt nivell a un Hamiltonià model mitjançant la teoria d’Hamiltonians efectius. Aquesta metodologia s’aplica a complexos de Ni(II), Co(II) i Mn(III) i es comprova que és aplicable de forma general a complexos mononuclears. S’estén després la metodologia a complexos binuclears, pels quals l’Hamiltonià model usualment utilitzat té una base menys rigorosa. L’Hamiltonià efectiu obtingut per un complex binuclear de Ni(II) introdueix una nova parametrització amb termes addicionals de les interaccions anisotròpiques en sistemes polinuclears. Es tracta d’un procediment universal que proporciona valors precisos i a més és capaç de contrastar la consistència interna dels Hamiltonians models existents. Per racionalitzar les correlacions magnetoestructurals dels paràmetres d’anisotropia en complexos de Ni(II) i Mn(III), es descriuen els mecanismes electrònics bàsics en base a consideracions de la teoria del camp del lligand. Aquest procediment proporciona regles senzilles per augmentar l’anisotropia, que poden ser aplicades en el disseny de nous materials. Finalment, s’estudien les interaccions anisotròpiques simètriques i antisimètriques en compostos binuclears de Cu(II), interaccions de gran importància per explicar les propietats d’alguns materials d’interès tecnològic. Les interaccions antisimètriques s’extreuen a partir de càlculs ab initio d’estructura electrònica per primer cop en aquest treball. Es concentra l’atenció d’aquesta part en dos sistemes: el conegut complex binuclear de Cu(II) amb quatre ponts acetat, i l’òxid de coure en el que recentment s’ha evidenciat una fase ferroelèctrica.

Solid-state NMR spectroscopy is used to investigate strong hydrogen bonds in a variety of solids. NMR measurements of the 2H nuclear quadrupole coupling (CQ) and nuclear magnetic shielding tensors are performed on samples of trimethylammonium chloride (TMAC), protonated 1,8-bis(dimethylamino)napthalene (DMANH+), and potassium and sodium bifluoride. 2H CPMAS is used to obtain high quality spectra while reducing experimental time. From spectral simulations, values of 127, 36, 59 and 58 kHz are determined for the 2H CQ of TMAC, DMANH+ CF3SO3-, NaHF2 and KHF2, respectively. The 2H CPMAS spectrum of TMAC shows a minor secondary component resulting from a solid phase in which the trimethylammonium cation is experiencing precessional motion. At high temperature the 2H CPMAS spectrum of DMANH+ shows unexpected spinning sideband lineshapes because of residual dipolar coupling to 14N. The experimental 2H CQ values are corroborated by ab-initio and DFT calculations; for DMAN and the bifluorides the 2H CQ values are averaged over the potential energy surface to improve the computational quality. Large values of the isotropic chemical shift (>10 ppm) are observed for all of the hydrogen-bonded deuterons. To complement the 2H NMR work, other nuclei in the compounds of interest are investigated, for TMAC these include: 35Cl, 37Cl, 1H, 14N, 15N. The 35Cl CQ shows a small, but observable deuterium/proton isotope effect. Quadrupolar and chemical shift parameters for assorted nuclei in TMAC are calculated at various N-H distances, demonstrating the strong dependence of the chlorine and hydrogen parameters on the proton position. For DMANH+ the 15N CPMAS spectrum of a static sample of DMANH+-d1 provides a value for the average dipolar 15N-D coupling constant of 870±30 Hz, corresponding to a distance of 1.29 A. Spectra of the counterions in the bifluoride salts are obtained, providing CQ values of 123 kHz and 1.141 MHz for 39K and 23Na, respectively.

Bakalauro baigiamojo darbo pirmojoje dalyje išanalizuoti krovininio 1,3 t galios keltuvo techniniai parametrai, darbo saugos lygis, nustatyta gamybos apimtis. Antroje darbo dalyje aprašyta gaminio paskirtis ir pradiniai duomenys. Atlikta krovininių keltuvų konstrukcijų variantų apţvalga – įvairių tipų krovininių keltuvų konstrukcijų sprendimų palyginimas. Pateiktas projektuojamojo krovininio keltuvo konstrukcijos aprašymas ir pagrindimas. Atlikti gaminio techniniai skaičiavimai (pagrindinių parametrų nustatymas, lyno ir pavaros skaičiavimas, lyno blokų ir tvirtinimo pirštų stiprumo skaičiavimas, lyno balansyrinės pakabos stiprumo skaičiavimas). Trečioje dalyje išanalizuota vienos detalės technologiniai maršrutai, nustatyti apdirbimo operacijoms reikalingi įrengimai. Atliktas uţlaidų, pjovimo rėţimų nustatymas bei techninis normavimas. Ketvirtojoje dalyje pateikiama techniniai ir eksploataciniai reikalavimai naudojant kėlimo įrenginį. Penktojoje dalyje atlikti ekonominiai skaičiavimai, kurių pagalba nustatyta ir pagrysta krovininio 1,3 t galios keltuvo savikaina. / The aim of the study is to design Cargo Lifter of 1,3 Ton Capacity. The first part of the bachelor‟s thesis analyses the main technical parameters of cargo lifter of 1,3 ton capacity, the level of labour safety and determines the scope of production. The second part describes the function of the product have been described, the versions of constructions of freight lifts have been reviewed, different construction solutions of various types of freight lifts have been compared in the second part. Description and justification of the construction of the designed freight lift has been provided, technical calculations of the product (definition of the main parameters, calculations of a rope and gear, calculation of strength of rope units and fastening pins, calculation of strength of a rope balance suspension) have been performed. The third part deals with the analysis of technological routes of a single part, determination of the installations necessary for processing operations as well as identification and technical rating of overlaps and cutting modes. In the fourth section presents the technical and operational requirements for using the lifting device. The fifth part deals with economic calculations on the basis of which the net cost of the freight lift of 1,3 t capacity has been determined and justified.