Browsing by Author "Himstedt, Kai"
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- KonferenzbeitragSimulation and Optimization as Modular Tasks within a Framework on High-Performance-Computing-Platforms(Proceedings of the 28th Conference on Environmental Informatics - Informatics for Environmental Protection, Sustainable Development and Risk Management, 2014) Wittmann, Jochen; Himstedt, Kai; Köhler, Steven; Möller, Dietmar P.F.In the context of the project „Effizienter Flughafen 2030“ separate, autarkic models simulating the different processes at an airport have been coupled to build an integrative over-all model. For scenario analysis and to identify the relevant model parameters for the over-all behavior it was postulated to fit input parameter values automatically with regard to a certain optimal behavior of the coupled system. To solve this task, a framework approach had been developed using softcomputing optimization methods. Independently of its original motivation and application, this approach can be applied to all complex optimization problems, if an encapsulated specification of the model components and the optimization is provided. The soft computing approach has the advantage to be able to deal easily with typical phenomena known in the area of environmental modeling such as lack of definition, non-linearity, or incomplete data. On the technical level it was a quite natural step to transfer the concept of the model coupling to the complete framework including the optimization component and to implement the complete functionality as a web service. For the prototype introduced in this paper genetic algorithms are selected for the optimization module. The architecture of the genetic solver demonstrates the general framework approach and is able to use high-performance-computing platforms to produce considerable speedups without demanding high bandwidths or low latency interconnections for the platform used. A simple application example will demonstrate the interfaces for the model and the genetic solver that have to be provided to encapsulate these components for usage in the framework. The outlook deals with the optimization of the parameters of the genetic solver itself and proposes to interpret the black-box web-service interface of the solver as a model itself such cascading two genetic solvers: the inner one to optimize the simulation model parameters and the outer one to optimize the genetic algorithm parameters of the inner one.
- KonferenzbeitragThe Concept for a Flexible Authoring and Learning Environment(Environmental Communication in the Information Society - Proceedings of the 16th Conference, 2002) Bach, Markus; Bergstedt, Stefan; Himstedt, Kai; Wiegreffe, Stefan; Wittmann, JochenThis paper describes the concept for a flexible authoring and learning environment and is presented at the workshop “Learning Systems for Environmental Informatics”. It starts defining the requirements for the important flexibility of learning systems in respect to the current background of the learner, the dynamic ordering in which content is presented to the learner – also with consideration of the individual progress a learner makes – and the opportunity for the learner to proceed on many different paths in an exploratory way of learning. To reach this flexibility it is required that a single page consists of several so called content units, which are arranged dynamically during runtime of a learning session. A page generator module controls the actual arrangement of the content units. The page generator gets its information from different components (i.e. databases) such as individual user data, a course program, a content unit library and so on. For a unified layout of the pages the content units are arranged on the base of (configurable) templates. The concept shows how the learning environment component is interconnected to the authoring component, course management component and administration component to build an integrated and complete system.