Catalytic applications of waste derived materials

Sustainability has become a watchword and guiding principle for modern society, and with it a growing appreciation that anthropogenic 'waste', in all its manifold forms, can offer a valuable source of energy, construction materials, chemicals and high value functional products. In the context of chemical transformations, waste materials not only provide alternative renewable feedstocks, but also a resource from which to create catalysts. Such waste-derived heterogeneous catalysts serve to improve the overall energy and atom-efficiency of existing and novel chemical processes. This review outlines key chemical transformations for which waste-derived heterogeneous catalysts have been developed, spanning biomass conversion to environmental remediation, and their benefits and disadvantages relative to conventional catalytic technologies

Mathematische Analyse mariner Ökosystemmodelle

This work is concerned with the mathematical formulation of marine ecosystem models. Marine ecosystem models are systems of advection-diffusion-reaction equations. The influence of biogeochemical reactions (e.g. consumption of nutrients, growth, decomposition) is modeled by reaction terms which are, in general, nonlinear functions of all regarded concentrations. The reaction terms additionally include parameters (e.g. growth rates). Parameter identification, i.e., the determination of parameter values, enables the model's adjustment to the ecosystem in question. Parameter identification is a mathematical optimization problem. In applications, the model equation and the parameter identification problem are solved numerically. A satisfying assessment of numerical solutions requires information about the continuous model. In this work, we investigate the continuous equation of a general ecosystem model and the corresponding parameter identification problem. As a result, we obtain the existence of transient and periodic solutions. To prove the existence of transient solutions, we rely on standard methods (Galerkin's method, Banach's Fixed Point Theorem) which we adapt to the nonlinearly coupled systems of equations and the two types of reaction terms. In the periodic case, we investigate models which are solved by the constant zero function. The existence result ensures that, in addition, nontrivial periodic solutions exist. Concerning parameter identification, we prove the existence of optimal parameters for quadratically integrable data. In addition, we indicate first and second order optimality conditions and formulate the first order condition as an optimality system. We apply all theoretical results to the PO4-DOP model which is important for testing purposes. By means of a numerical test based on a two-dimensional version of the PO4-DOP model, we investigate uniqueness of numerically computed periodic solutions

Augmented Reality for Machine Maintenance Applications

Nowadays, organizations have to cope with different challenges, such as varying factors concerning the requirements of the markets, products, and services. Therefore, organizations have to constantly improve their business processes to keep up with these varying demands. For instance, the maintenance processes of a machinery and physical systems may have many different procedures depending on external process factors (such as customer requirements and specifications) and internal factors (i.e., utilized machines, machine types, attrition of machine parts, knowledge level of a maintenance operator). Ultimately, used process management concepts and systems have to support variability and context data management during modeling and execution time. This thesis develops a context- and process-aware information system to support maintenance operators with their daily work tasks. Thereby, augmented reality is used for interaction between a maintenance operator and the developed proof-of-concept implementation. The latter acquires sensor data from different information systems, executes and adapts executed process based on the current contextual situation, and visualizes augmented guidelines to maintenance operators in real time. By using such a context-aware process information system during a maintenance routine, organizations are able to improve quality and time efficiency of a maintenance routine