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Den Helder, Netherlands

Notenboom R.P.,Netherlands Defense Academy | Arbocz J.,Technical University of Delft
AIAA Journal

The Sanders shell equations for imperfect anisotropic circular cylindrical shells are used for the development of a research tool to study the nonlinear interaction of circumferential waves under different loading conditions. Therefore, a truncated Fourier series in circumferential direction is used as a possible solution of the nonlinear equilibrium equations in combination with the anisotropic constitutive relations. The envelope of the Fourier series coefficients in the axial direction is computed using a numerical integration technique satisfying the rigorous boundary conditions at the lower and upper shell edges. The case of an isotropic shell under axial compression is used to compare the results obtained by the current theory and the STAGS-A program. Copyright © 2010 by R. P. Notenboom and J. Arbocz. Published by the American Institute of Aeronautics and Astronautics, Inc. Source

Plasmeijer R.,Radboud University Nijmegen | Lijnse B.,Radboud University Nijmegen | Lijnse B.,Netherlands Defense Academy | Michels S.,Radboud University Nijmegen | And 2 more authors.
PPDP'12 - Proceedings of the 2012 ACM SIGPLAN Principles and Practice of Declarative Programming

Task-Oriented Programming (TOP) is a novel programming paradigm for the construction of distributed systems where users work together on the internet.When multiple users collaborate, they need to interact with each other frequently. TOP supports the definition of tasks that react to the progress made by others. With TOP, complex multi-user interactions can be programmed in a declarative style just by defining the tasks that have to be accomplished, thus eliminating the need to worry about the implementation detail that commonly frustrates the development of applications for this domain. TOP builds on four core concepts: tasks that represent computations or work to do which have an observable value that may change over time, data sharing enabling tasks to observe each other while the work is in progress, generic type driven generation of user interaction, and special combinators for sequential and parallel task composition. The semantics of these core concepts is defined in this paper. As an example we present the iTask3 framework, which embeds TOP in the functional programming language Clean. Copyright © 2012 ACM. Source

Hoencamp A.,Netherlands Defense Academy | D.Pavel M.,Technical University of Delft
Journal of the American Helicopter Society

Qualification programs to define ship-helicopter operational limitations are based on a large number of independent variables causing the full operational potential to be almost impossible to achieve within the small window normally allowed for sea trials. It would be a clear advantage to have a predictive engineering tool to perform early evaluations of safety limits for operating aircraft from ships in a wide range of in-service conditions, and so be less dependent on the dedicated sea trials. For this reason, a predictive analysis tool, SHOL-X, is under development based on specific rejection criteria for each helicopter type and their dependencies in the ship environment. The object of this paper is to describe the concept of such a tool that can be used for determining the so-called candidate flight envelope for a helicopter operating on a certain ship type. This tool enables performing larger operational steps in an incremental approach toward defining flight envelope restrictions and sensible exclusion of test points. The prediction accuracy of this analysis tool allows advanced insight into cost effectiveness of complete sea trials and ultimately certification of large parts of the envelope with a reduction in the amount of sea trials. © 2012 The American Helicopter Society. Source

Lijnse B.,Radboud University Nijmegen | Lijnse B.,Netherlands Defense Academy | Plasmeijer R.,Radboud University Nijmegen
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Workflow management systems (WFMSs) are systems that generate, coordinate and monitor tasks performed by human workers in collaboration with automated (information) systems. The iTask system (iTask) is a WFMS that uses a combinator language embedded in the pure and lazy functional language Clean for the specification of highly dynamic workflows. iTask workflow specifications are declarative in the sense that they only specify (business) processes and the types of data involved. They abstract from user interface and storage issues, which are handled generically by the workflow engine. Earlier work has focused on the development of the iTask combinator language. The workflow language was implemented as an engine that evaluated task combinator expressions and generated interactive web pages. Although suitable for its original purpose, this architecture has proven to be less so for generating practically usable workflow support systems. In this paper we present a new implementation of the iTask system that implements the combinator library using a service based architecture that exposes the workflow and a user friendly Ajax client. Because user interface issues are outside the scope of workflow specifications, and cannot be specified explicitly, it is crucial that the generic operationalization of the declarative interaction primitives is of adequate quality. We explain the novel generic libraries we have developed for this purpose. © 2010 Springer-Verlag. Source

Somsen O.J.G.,Netherlands Defense Academy
Wireless Personal Communications

Studies of wireless networks often work with a relatively high communication range so that each node typically communicates with a high number of neighbors. This is necessary, with a random placement, to avoid loss of coverage or connectivity. However, communicating through remote neighbors requires more energy, which can be a severe disadvantage since energy is often critical in this type of network. By comparing two-ranges, one to ensure coverage and one to save energy, we identify link-nodes which play an essential role to keep the network connected. Characterizing these nodes and their occurrence in communication routes will help to save energy and increase lifetime of the overall network. Without precautions, these link-nodes receive a high traffic load. Using simulations we find that slightly longer routes can avoid link-nodes and thus reduce average energy consumption. Network lifetime can be extended by identifying these nodes at startup and reducing their energy consumption wherever possible. © 2013 Springer Science+Business Media New York. Source

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