Modellierung in der Softwaretechnik

Ohne Zusammenfassung     

Reduction of the porcelain firing temperature by preparation of the raw materials

An innovative way of reduction of firing temperature of porcelain tableware is reached by preparation of raw materials down to submicron- and nanoscaled powder for higher reactivity. In this study a common slurry was ground in an agitator ball mill from d₅₀ = 5.0 μm to 0.9 μm, green bodies were prepared, and glost firing was simulated in a dilatometer. The sintering temperature has been decreased by approximately 180 °C. A reflection between ball mill and agitator ball mill regarding the grinding cost shows no difference which means that the ball mill could be replaced. The energy consumption during the grinding process will be discussed regarding to energy savings resulting from reduced firing temperature. Furthermore a comparison between experimental and literature data will be done. The effect of grinding of raw material is finally evaluated concerning sintering behaviour and material properties.     

The cell average technique for solving multi-dimensional aggregation population balance equations

In this paper, the cell average discretization [Kumar, J., Peglow, M., Warnecke, G., Heinrich, S., & Mörl, 2006a. Improved accuracy and convergence of discretized population balance for aggregation: The cell average technique. Chemical Engineering Science, 61, 3327–3342] is extended to solving multi-dimensional population balance equations. Similar to the one-dimensional case, the scheme is based on an accurate prediction of certain moments of the population. The formulation is quite simple to implement, computationally not expensive and highly accurate. Numerical diffusion is a common problem with many numerical methods when applied on coarse grids. The presented technique nearly eliminates numerical diffusion and predicts four moments (zeroth, first, first cross and second) of the distribution function with high accuracy. The technique may be implemented on any type of grid. The accuracy of the scheme has been analyzed by comparing analytical and numerical solutions of three test problems. The numerical results are in excellent agreement with the analytical results and show the ability to predict higher moments very precisely. Additionally, an extension of the proposed technique to higher dimensional problems is discussed.     

Deriving static and dynamic concepts from software requirements using sophisticated tagging

Natural language requirements specifications form the basis for the subsequent phase of the information system development process, namely the development of conceptual schemata. Both, the textual as well as the conceptual representations are not really appropriate for being thoroughly captured and validated by the ‘requirement holders’, i.e. the end users. Therefore, in our approach the textual specifications are firstly linguistically analyzed and translated into a so-called conceptual predesign schema. That schema is formulated using an interlingua which is based on a lean semantic model, thus allowing users to participate more efficiently in the design and validation process. After validation, the predesign schema is mapped to a conceptual representation (e.g. UML). The sequence of these translation and transformation steps is described by the “NIBA workflow”. This paper focuses on the information supporting a step by step mapping of natural language requirements specifications to a conceptual model, and on how that information is gained. On particular, we present a four-level interpretation of tagging-output.     

Ranking and selection of power expansion alternatives for multiple objectives under uncertainty

Strategic planning in the electricity supply industry is a complex task due to the multiple and often conflicting objectives of the decision makers, as well as the inherent technical and valuation uncertainties involved. As such, a transparent decision support framework is needed, for guiding information management throughout the decision process, in a way which shapes decision outcomes, and enables confident choices to be made. This paper outlines a methodology for the ranking of power expansion alternatives given multiple objectives and uncertainty, and demonstrates this using the South African electricity supply industry. This methodology uses a value function MCDA approach that is augmented with scenario analysis to yield information relating to both the relative performance and credibility of power expansion alternatives. A portfolio of preferred alternatives is then identified based on performance and confidence criteria. Finally a more detailed analysis of the reduced solution set examines short-term technology investment details alongside attribute performance information, so as to gain insight into the decision problem and relate it back to real life actions.     

Bipolar model extension for MOS transistors considering gate coupling effects in the HBM ESD domain

The presented compact model for NMOS transistors combines both the high-current bipolar mode and the MOS mode considering modulation of the current gain β and gate coupling effects. For the studied 0.35 μm-CMOS devices, measurement and simulation correlate very well with respect to layout variations, fulfilling a prerequisite for the simulation guided synthesis and optimization of ESD protection structures and schemes. The open model interface also allows the use of existing proprietary MOS-models.     

织袜机钩针的局部变形

在研究项目的范围内研究了女士连裤袜中出现块状/纵向条纹的原因.结果表明针织机上的几个问题导致了钩针的针钩区几何形变.     

Numerical calculation of the electronic structure for three-dimensional quantum dots

In some recent papers Li, Voskoboynikov, Lee, Sze and Tretyak suggested an iterative scheme for computing the electronic states of quantum dots and quantum rings taking into account an electron effective mass which depends on the position and electron energy level. In this paper we prove that this method converges globally and linearly in an alternating way, i.e. yielding lower and upper bounds of a predetermined energy level in turn. Moreover, taking advantage of the Rayleigh functional of the governing nonlinear eigenproblem, we propose a variant which converges even quadratically thereby reducing the computational cost substantially. Two examples of finite element models of quantum dots of different shapes demonstrate the efficiency of the method.     

Efficient stochastic simulation of thermal spray processes

Thermal spray processes allow the production of coatings with a wide variety of useful properties, and therefore are used in a lot of different industrial applications. However, in specific applications, it can be a challenging and time consuming task to tune the parameters of a thermal spraying system so that required surface properties, such as wear- , corrosion- or heat resistance, can be achieved. Computer-aided stochastic simulations of thermal spray processes try to overcome these problems by modelling the coating build-up on a per-droplet basis, and by deriving the properties of interest from the generated structure afterwards. Because of the large number of droplets that need to be treated during the simulation to generate a sufficiently large virtual coating, the use of efficient algorithms is essential. On the other hand more complex algorithms are needed to increase the accuracy of the simulation.In this report we present novel extensions to a simulation model by Ghafouri et al. concerning plasma spraying. The extensions include a physically inspired splat spreading approach, a method to generate splat fingers, and a filtering technique that allows for the calculation of pores below overlapping splats. Furthermore, features characterizing coatings beyond the commonly used porosity or surface roughness are presented and analyzed with respect to their appropriateness. Features are considered appropriate if they are depending in a unique way on the parameters of the simulation model. This kind of features might be used in an automatic adaptation of the simulation model to real processes. Finally, several contributions are made in order to increasing the computational efficiency of the simulation. Most important, dexel models are introduced to represent the coating.