Dyson--Schwinger Approach to Hamiltonian QCD

Dyson--Schwinger equations are an established, powerful non-perturbative tool for QCD. In the Hamiltonian formulation of a quantum field theory they can be used to perform variational calculations with non-Gaussian wave functionals. By means of the DSEs the various $n$-point functions, needed in expectation values of observables like the Hamilton operator, can be thus expressed in terms of the variational kernels of our trial ansatz. Equations of motion for these variational kernels are derived by minimizing the energy density and solved numerically.Comment: Talk given by D. Campagnari at XIIth Quark Confinement and the Hadron Spectrum, August 28-September 04, 2016, Thessaloniki, Greece, submitted to the proceeding

Variationszugang zur QCD in Coulombeichung

Diese Arbeit behandelt die QCD im Variationszugang in Coulombeichung. Mithilfe dieser nicht-perturbativen Methodik wird der Vakuumzustand der QCD mithilfe eines Ansatzes approximativ bestimmt und der phänomenologische Wert des chiralen Quarkkondensats exakt reproduziert. Die Erweiterung auf endliche Temperaturen wird durch Kompaktifizieren einer räumlichen Dimension durchgeführt und liefert realistische Werte für den QCD-Phasenübergang

The Analyses of the Rate of Pitting Corrosion of a NiTi Rod in a Natural Marine Environment

The analysis of the behaviour of new materials in the natural environment is important for their application and commercial use. In order to explore the application of Shape Memory Alloys in the Maritime industry, this research focuses on the corrosive behaviour of the NiTi rod that was produced by means of a continuous casting process. The experiment included three samples of NiTi rods that were exposed to the marine environment for 6, 12 and 18 months at a depth of 3 metres below the surface. The morphological and chemical changes were analysed separately during the experiment. Ultrasonic thickness equipment and the Scanning Electron Microscope (SEM) technique were used for the tests that determined the corrosion rates and detected pitting. The changes in the chemical composition of the NiTi rod were investigated by means of an Energy Dispersive X-ray (EDX) analysis, in order to define the pitting behaviour of the rod`s surfaces during its exposure to seawater. The obtained research results prove that the rate of pitting corrosion follows a progressive curve – the minimum value of corrosion rate equalled 0.04 mm/month, while the maximum value was 0.12 mm/month

A Framework for Simulation Models of Service-Oriented Architectures

Abstract Service-Oriented Architectures (SOA) are one of the main paradigms for future software systems. Since these software systems are composed of a large number of different components it is non trivial to assure an adequate Quality of Service (QoS) of the overall system and performance analysis becomes an important issue. To consider performance issues early in the development process, a model based approach becomes necessary which has to be embedded into the development process of SOA to avoid overhead and assure consistency. In particular the specification of the software system should be used as a base for the resulting performance model. However, since common specification techniques for SOA are very high level, many details have to be added to come to an executable simulation model which is often needed for a detailed analysis of performance or dependability. This paper presents an approach which combines an extended version of process chains to describe the SOA components and some quantitative specifications at the higher levels. For the modelling of the detailed architecture and protocols the simulation tool OMNeT++ is used. Both modelling levels are combined resulting in an executable simulation model for the whole architecture

Simulating Process Chain Models with OMNeT++.

Abstract This paper presents an approach to simulate complex hierarchical process chains resulting from large logistics networks in OMNeT++, a discrete event simulation environment designed for communication networks. For this purpose OMNeT++ has been integrated as a new simulation engine into the ProC/B toolset which is designed for the analysis and optimization of large logistics networks. The paper highlights the main steps of the automatic transformation of a hierarchical process chain model into a hierarchical model in OMNeT++. Furthermore it shows how the transformation has been validated and how detailed performance figures can be evaluated with OMNeT++

Multivariate Regression Analysis of the NiTi Alloys’ Surface Corrosion Depending on the Measured Oxygen Value: Tests in Three Different Marine Environments

Actual corrosion experiments are based mainly on methodologies that measure the corrosion rate of alloys as a function of the parameters that characterise different external influences and the specific environment in which the alloys are placed. Corrosive processes are viewed as complex stochastic processes described by linear and nonlinear probabilistic models. In contrast to these common ways of analysing corrosive processes, this paper investigates the corrosion process in terms of chemical changes in the alloys’ surface compositions. For this purpose, two NiTi Shape Memory Alloys obtained by different technological production processes were tested, followed by an analysis of the empirical data obtained in a real experiment that included monitoring the corrosion behaviour. Both the analysed alloys were exposed to three different types of marine environment: air, tide, and sea. Data were collected continuously after 6, 12 and 18 months of samples’ exposure to the marine environmental influences. A total of six empirical databases were formed, one for each of the observed NiTi alloys in each of the three observed environments. The empirical databases systematised the data related to the measurements of the surface chemical composition obtained using Energy Dispersive X-ray (EDX) and Focused Ion Beam (FIB) analyses. Statistical analysis was performed to determine the correlation between the corrosion depth and the percentage of oxygen in the sample surfaces as well as to determine the similarities and differences in the corrosive behaviour of the two observed alloys in different marine environments