Air Force Institute of Technology Research Report 1997

This report summarizes the research activities of the Air Force Institute of Technology\u27s Graduate School of Engineering and the Graduate School of Logistics and Acquisition Management. It describes research interests and faculty expertise; list student theses/dissertations; identifies research sponsors and contributions; and outlines the procedure for contacting either school

Intelligent Simulation Modeling of a Flexible Manufacturing System with Automated Guided Vehicles

Although simulation is a very flexible and cost effective problem solving technique, it has been traditionally limited to building models which are merely descriptive of the system under study. Relatively new approaches combine improvement heuristics and artificial intelligence with simulation to provide prescriptive power in simulation modeling. This study demonstrates the synergy obtained by bringing together the "learning automata theory" and simulation analysis. Intelligent objects are embedded in the simulation model of a Flexible Manufacturing System (FMS), in which Automated Guided Vehicles (AGVs) serve as the material handling system between four unique workcenters. The objective of the study is to find satisfactory AGV routing patterns along available paths to minimize the mean time spent by different kinds of parts in the system. System parameters such as different part routing and processing time requirements, arrivals distribution, number of palettes, available paths between workcenters, number and speed of AGVs can be defined by the user. The network of learning automata acts as the decision maker driving the simulation, and the FMS model acts as the training environment for the automata network; providing realistic, yet cost-effective and risk-free feedback. Object oriented design and implementation of the simulation model with a process oriented world view, graphical animation and visually interactive simulation (using GUI objects such as windows, menus, dialog boxes; mouse sensitive dynamic automaton trace charts and dynamic graphical statistical monitoring) are other issues dealt with in the study

Aeronautical engineering: A continuing bibliography with indexes (supplement 238)

This bibliography lists 458 reports, articles, and other documents introduced into the NASA scientific and technical information system in March, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Hybrid modelling methodology for system design

In the face of rapid development in information technology coupled with a growing dynamism in global markets, manufacturing systems have to be re-constructed for short term or long term goal. Such innovations promise to lead to a new competitive stage, which typically involve design of function, information and behaviour of systems. In order to design the system, simulation has often been chosen. However, simulation has proved limited and fails to aid design of such a complex systems because of consuming much computing time and cost, especially when modelling larger systems. Thus, there is a need to seek a new approach, in a way that results in simulating such a large manufacturing system with less demand on computing time and cost. This study researches into a hybrid modelling approach to minimise these limitations. It includes proposing a hybrid modelling methodology and developing a hybrid modelling tool. The methodology integrates simulation and metamodelling techniques. The metamodel employed in the study possesses, not only characteristics of conventional metamodels in terms of representing relationships in quantity, but also in time lapse. This is the originality of the study and the significant distinction between this research and application of metamodelling in conventional ways. The hybrid modelling tool is developed to support and demonstrate the identified hybrid methodology. LISP has been used as the software language for the hybrid modelling tool. The result of this work concludes that the hybrid modelling approach is capable of simulating a complex manufacturing system with less demands on the computer. The work reported in this thesis has been carried out in conjunction with the EPSRC research project, Hierarchical Manufacturing System Modelling (HMSM) (GR/F96549), to produce an Integrated Design and Modelling Methodology (IDEM). The project was initially a collaborative research program including Loughborough University of Technology (LUT), Morris Crane Ltd., of Loughborough and GEC Large Machine, of Rugby. The experience of these collaborators has proved most valuable in supporting the research, and have provided a cross section of views and comments. The research reported in this thesis is set in the context of the HMSM Research group at Loughborough

Dustbowl Legacies: Long Term Change and Resilience in the Shortgrass Steppe

http://deepblue.lib.umich.edu/bitstream/2027.42/61279/1/Sylvester.Gutmann.dustbowl legacies.pd

Parallel and Distributed Computing

The 14 chapters presented in this book cover a wide variety of representative works ranging from hardware design to application development. Particularly, the topics that are addressed are programmable and reconfigurable devices and systems, dependability of GPUs (General Purpose Units), network topologies, cache coherence protocols, resource allocation, scheduling algorithms, peertopeer networks, largescale network simulation, and parallel routines and algorithms. In this way, the articles included in this book constitute an excellent reference for engineers and researchers who have particular interests in each of these topics in parallel and distributed computing

The analysis of coral reef resilience - a generic modelling tool

Coral reefs, rainforests of the sea, are of greatest ecological and economical importance. Although they cover just a small fraction of sea floor, they provide indispensable functions for the associated flora and fauna, and invaluable services for livelihoods of large human populations in tropical coastal regions. Within the last few decades coral reefs have been increasingly endangered for various reasons, which can be directly or indirectly ascribed to anthropogenic influence. Chronic stresses can undermine the resilience of coral reefs, which then become more susceptible to the effects of pulse stresses, like hurricanes or thermally induced bleaching. Such an event may then diminish relevant ecosystem properties beyond a threshold, and thus trigger a sudden shift to an alternative state, which may not be in favour of corals but an alternative live form that then achieves dominance. In my thesis I developed a spatially explicit individual-based model to simulate a benthic reef community, typical for a reef in the Western Indian Ocean region. The application was then used to explore key variables and -processes for resilience and to identify potential triggers for phase shifts. Several coral species with contrasting life histories and algae compete for space under different environmental influences. Evoked by direct neighbourhood-interactions and individual responses to environmental conditions, the system performs dynamic self-organisation, and properties of superordinate hierarchical levels (population, community) emerge as a consequence. In multiple scenarios I tested the influences of (i) two different perturbation types (bleaching and mechanical disturbances), -intensities and frequencies, as well as (ii) various levels of grazing and recruitment on the dynamics of coral reef communities. As the results show, perturbations can generate heterogeneous outcomes. While extreme temperature events render a disadvantage for more susceptible branching coral species, these species can dominate under high frequencies of mechanical disturbance events, because they recolonize empty space faster, due to their faster growth rates. Low disturbance levels always benefit the dominance of massive growth forms and a combination of both perturbations at intermediate levels leads to high evenness in the community composition. The results additionally confirm, that herbivory and recruitment are crucial processes for the resilience and persistence of coral reefs. This study also highlights the importance of a diversified analysis of coral reef dynamics to understand the full magnitude of consequences, caused by environmental change. The presented application renders an excellent tool (a) to integrate current knowledge, which can be kept up to date with little effort and (b) can be coupled with other modelling systems that operate on different spatial and temporal scales. Complexity and non-linear dynamics of coral reef functioning can thus be simulated and analysed with a high level of detail and informative value

An Exploration of Enterprise Architecture Research

Management of the enterprise architecture has become increasingly recognized as a crucial part of both business and IT management. Still, a common understanding and methodological consistency seems far from being developed. Acknowledging the significant role of research in moving the development process along, this article employs different bibliometric methods, complemented by an extensive qualitative interpretation of the research field, to provide a unique overview of the enterprise architecture literature. After answering our research questions about the collaboration via co-authorships, the intellectual structure of the research field and its most influential works, and the principal themes of research, we propose an agenda for future research based on the findings from the above analyses and their comparison to empirical insights from the literature. In particular, our study finds a considerable degree of co-authorship clustering and a positive impact of the extent of co-authorship on the diffusion of works on enterprise architecture. In addition, this article identifies three major research streams and shows that research to date has revolved around specific themes, while some of high practical relevance receive minor attention. Hence, the contribution of our study is manifold and offers support for researchers and practitioners alike

Proceedings, MSVSCC 2017

Proceedings of the 11th Annual Modeling, Simulation & Visualization Student Capstone Conference held on April 20, 2017 at VMASC in Suffolk, Virginia. 211 pp