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System dynamics is an approach to understanding the behaviour of complex systems over time. It deals with internal feedback loops and time delays that affect the behaviour of the entire system. What makes using system dynamics different from other approaches to studying complex systems is the use of feedback loops and stocks and flows. These elements help describe how even seemingly simple systems display baffling nonlinearity. Wikipedia.

Ossmann D.,System Dynamics
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

The reliable detection of faults located in the control loop of safety critical systems is an important aspect in reducing potential hazards induced by possible faults. Any fault detection and diagnosis system for a safety critical system has to fulfill strong safety specifications which can be expressed in terms of different performance criteria as detection time performance, missed detection rate, or false alarm rate. To satisfy all design requirements in the presence of unknown external signals and parametric uncertainties a tuning of the free parameters in the fault detection and diagnosis system often becomes necessary after the design of residual filters. In this paper an advanced approach to tune these free parameters based on a multi objective parameter optimization setup is presented. © IFAC. Source

Aoki S.,University of Tokyo | Ito M.,University of Tokyo | Iwasaki W.,System Dynamics
Molecular Biology and Evolution | Year: 2013

Although many α- And some β-proteobacterial species are symbiotic with legumes, the evolutionary origin of nitrogenfixing nodulation remains unclear. We examined α- And β-proteobacteria whose genomes were sequenced using largescale phylogenetic profiling and revealed the evolutionary origin of two nodulation genes. These genes, nodI and nodJ (nodIJ), play key roles in the secretion of Nod factors, which are recognized by legumes during nodulation.We found that only the nodulating β-proteobacteria, including the novel strains isolated in this study, possess both nodIJ and their paralogous genes (DRA-ATPase/permease genes). Contrary to the widely accepted scenario of the α-proteobacterial origin of rhizobia, our exhaustive phylogenetic analysis showed that the entire nodIJ clade is included in the clade of Burkholderiaceae DRA-ATPase/permease genes, that is, the nodIJ genes originated from gene duplication in a lineage of the β-proteobacterial family. After duplication, the evolutionary rates of nodIJ were significantly accelerated relative to those of homologous genes, which is consistent with their novel function in nodulation. The likelihood analyses suggest that this accelerated evolution is not associated with changes in either nonsynonymous/synonymous substitution rates or transition/transversion rates, but rather, in the GC content. Although the low GC content of the nodulation genes has been assumed to reflect past horizontal transfer events from donor rhizobial genomes with low GC content, no rhizobial genome with such low GC content has yet been found. Our results encourage a reconsideration of the origin of nodulation and suggest new perspectives on the role of the GC content of bacterial genes in functional adaptation. © The Author 2013. Source

Levis S.,System Dynamics
Wiley Interdisciplinary Reviews: Climate Change | Year: 2010

Land surfacemodelingwas invented to represent the atmosphere's lower boundary over continental areas in climate models. Mass, momentum, and energy cross this boundary via biogeochemical and biogeophysical processes often involving plants. Scientific research with models and in the field strives to refine how the changing face of the land interacts with climate change. Discussed here are methods by which we simulate the vegetation and land use in global models and ways by which vegetation and land use affect climate. Model simulations suggest that global land cover changes due to land use play a greater role in affecting 20thand 21st-century climate than changes in unmanaged vegetation. Among the biogeochemical and biogeophysical effects of land use, biogeochemical ones seem to dominate and enhance 20th- and 21st- century warming. Among the effects of natural vegetation, the positive biogeophysical snow-vegetation-albedo feedback of the high latitudes is expected to increasingly influence global climate in response to increasing vegetation density. Still, human or natural disturbances and other not well-understood processes may alter expected outcomes. Interactive nitrogen is one of the newer additions to our models. Nitrogen is found to buffer the terrestrial biosphere's response to forcings, such as changing CO 2 or climate. We still have much to learn about nitrogen's role in the Earth System. Yet, if land use dominates the effects of land cover change on climate, then human behavior will be our greatest uncertainty, which includes management choices that are not easy to predict, such as urbanization, deforestation and afforestation, crop expansion or abandonment, as well as crop rotation, irrigation, and fertilization. © 2010 John Wiley & Sons, Ltd. Source

Shigarov A.O.,System Dynamics
Expert Systems with Applications | Year: 2014

The paper discusses issues on the conversion of tabular data from unstructured to structured form. Particularly, we propose an approach to table understanding (i.e. recovering semantic relationships in a table), which is designed for unstructured tabular data integration. Our approach is based on using a rule engine. It is assumed that spatial, style (typographical), and natural language information can be used for table analysis and interpretation. The CELLS system based on the approach has been developed for integrating unstructured tabular data presented in Excel spreadsheet format. Experimental results show that the approach and system can be applied to a wide range of tables from statistical and financial reports. © 2014 Elsevier Ltd. All rights reserved. Source

System Dynamics | Date: 2012-10-01

A method of controlling a combination vehicle for road transport of heavy goods, said vehicle comprising a motor vehicle at the front and a trailer attached so as to be towed behind the motor vehicle, said trailer comprising:

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