Model updating using uncertain experimental modal data

The propagation of parameter uncertainty in structural dynamics has become a feasible method to determine the probabilistic description of the vibration response of industrial scale �nite element models. Though methods for uncertainty propagation have been developed extensively, the quanti�cation of parameter uncertainty has been neglected in the past. But a correct assumption for the parameter variability is essential for the estimation of the uncertain vibration response. This paper shows how to identify model parameter means and covariance matrix from uncertain experimental modal test data. The common gradient based approach from deterministic computational model updating was extended by an equation that accounts for the stochastic part. In detail an inverse approach for the identi�cation of statistical parametric properties will be presented which will be applied on a numerical model of a replica of the GARTEUR SM-AG19 benchmark structure. The uncertain eigenfrequencies and mode shapes have been determined in an extensive experimental modal test campaign where the aircraft structure was tested repeatedly while it was 130 times dis- and reassembled in between each experimental modal analysis

Potential impacts on important bird habitats in Eiderstedt (Schleswig-Holstein) caused by agricultural land use changes

Agricultural land on the Eiderstedt peninsula in Schleswig-Holstein (Germany) is traditionally dominated by extensively used grassland. These grassland areas are home to many (endangered) bird species, making Eiderstedt one of the prime bird habitats at the West coast of Schleswig-Holstein. Plans exist to convert large shares of grassland to arable farm land to grow crops needed in an intensified dairy production and for biofuels. In this study, three possible scenarios of agricultural land use change on Eiderstedt in the next couple of decades are developed. Using a GIS the possible impacts of such conversions on breeding bird populations of four key species are determined. The results indicate that an increase of arable farm land to approximately two thirds of the whole agricultural area drastically reduces suitable bird habitat, thus considerably diminishing the number of breeding pairs supported by the environment. The ornithological impact is greatest if conversion takes place throughout Eiderstedt extending from already existing areas of arable farm land. But even though the reduction in suitable breeding habitat is less pronounced in the other scenarios, every one of them induces a severe pressure on populations of meadowbirds that rely on habitat on Eiderstedt for successful reproduction.land use

Possible Economic Impacts of a Shutdown of the Thermohaline Circulation: an Application of FUND

Climate change can lead to a substantial reduction of the strength of the thermohaline circulation in the world oceans. This is often thought to have severe consequences particularly on the North Atlantic region and Northern and Western Europe. The integrated assessment model FUND is used to estimate the extent of these impacts. The results indicate that, owing to a slower warming (rather than cooling) of the regions most affected by a thermohaline circulation collapse, climate change induced damages in these regions would be smaller in case of a shutdown of the thermohaline circulation. However, even with a thermohaline circulation collapse, the total and marginal impacts of climate change are negative.climate change, climate change impacts, thermohaline circulation, integrated assessment

Economic impacts of changes in population dynamics of fish on the fisheries in the Barents Sea

A bioeconomic simulation model of the two interacting fish species cod (Gadus morhua) and capelin (Mallotus villosus) and their fisheries is presented and applied to assess the consequences of changes in the population dynamics of these important fish stocks in the Barents Sea. In each scenario, the population dynamics of the fish species are changed by an external reduction of the reproductive rates and/or the carrying capacities. The stock sizes and landings of fish are calculated for each fishing period and the net present values of profits from fishing are determined for time periods prior to and after the change in population dynamics. Results show that reduced growth rates or carrying capacities both lead to lower stock levels and consequently to smaller catch sizes. There is only a small short-term economic impact on the fisheries but the long-term consequences are quite pronounced. In some cases, a higher fishing activity in the first few years after the change in population dynamics causes harvest sizes to remain stable despite diminishing stock sizes. This stabilizes the returns from fishing in the short run but veils the apparent negative long-term impact on the fisheries resulting from adversely affected stock dynamics.Barents Sea, bioeconomic modeling, capelin, cod, population dynamics

The economic impact of a shutdown of the Thermohaline Circulation: an application of FUND

The integrated assessment model FUND 2.8n is applied in an analysis of the overall economic consequences in a scenario of a shutdown of the thermohaline circulation (THC). Monetized market and non-market impacts of changes in environmental conditions following a THC collapse are determined for 207 individual countries. Eight different response patterns can be identified. The dominant pattern is that a THC shutdown has an offsetting effect on the underlying warming trend. Depending on whether the impacts of warming are initially beneficial or detrimental, the economic effects of a THC collapse show distinct regional variability. Key economic sectors affected in a THC shutdown scenario are water resources and energy consumption, as well as cardiovascular and respiratory diseases among health impacts. The maximum, national impact of a collapse of the THC turns out to be of the magnitude of a few per cent of GDP, but the global impact is much smaller. Considering the low probability of occurrence, a THC shutdown does not call for drastic action at present.Fisheries, climate change

Die biologische Vielfalt Mittelpolens im Wandel : Lässt sich Biodiversität auch unter veränderten agrarpolitischen Bedingungen erhalten?

Nach dem Beitritt Polens und weiterer Mittel-Osteuropäischer Staaten zur Europäischen Union (EU) am 1. Mai 2004 haben sich die politischen und administrativen Rahmenbedingungen dieser Länder grundlegend verändert. Um auf dem europäischen und auf dem Weltagrarmarkt bestehen zu können, ist für die ländlichen Räume der Beitrittsstaaten mit einem ausgeprägten Strukturwandel zu rechnen. Dieser Anpassungsprozess bringt – neben der Effizienzsteigerung für die Landwirtschaft – negative Auswirkungen auf die Biodiversität und die agrarische Nutzungsdiversität mit sich. Wie die Erfahrungen mit dem Wandel der Agrarstruktur in Mittel- und Westeuropa zeigen, sind davon zunächst kleinstrukturierte, traditionell wirtschaftende Familienbetriebe in – aus betriebswirtschaftlicher und naturräumlicher Sicht - ungünstigen Landschaften betroffen

Economic impacts on key Barents Sea fisheries arising from changes in the strength of the Atlantic thermohaline circulation

A bioeconomic model of key fisheries of the Barents Sea is run with scenarios generated by an earth system model of intermediate complexity to assess how the Barents Sea fisheries of cod (Gadus morhua) and capelin (Mallotus villosus) are affected by changes in the Atlantic thermohaline circulation arising from anthropogenic climate change. Changes in hydrographic conditions have an impact on recruitment success and survival rates which constitute a lasting effect on the stocks. The economic development of the fisheries is assessed for the 21st century, considering both adaptive and profit-maximizing harvesting strategies. Results show that a substantial weakening of the THC leads to impaired cod stock development, causing the associated fishery to become unprofitable in the long run. Simultaneous improvements in capelin stock development help the capelin fishery, but are insufficient to offset the losses incurred by the cod fishery. A comparison of harvest strategies reveals that in times of high variability in stock development, profit maximization leads to more stable economic results of these fisheries than the adaptive fishing strategy.Fisheries, climate change

Forest, Animal, and Seasonal Cycles Observed in Vernal Ponds at Audubon Center

Observations of environmental conditions and biota in four depressed spots, called vernal ponds , within the Northwoods Audubon Center near Sandstone, Minnesota, are reported for the period March 15 to September 4, 1977. Life cycle dynamics and utilization of the pond areas are considered in relation to time, days of the month, moisture-dryness, and species; but are lumped together for reporting as if the four locations were a single pond entity. Hypotheses as to the role of these ponds in the surrounding ecosystem and questions for possible further investigation are suggested

New Concepts in Pacemaker Syndrome

After implantation of a permanent pacemaker, patients may experience severe symptoms of dyspnea, palpitations, malaise, and syncope resulting from pacemaker syndrome. Although pacemaker syndrome is most often ascribed to the loss of atrioventricular (A-V) synchrony, more recent data may also implicate left ventricular dysynchrony caused by right ventricular pacing. Previous studies have not shown reductions in mortality or stroke with rate-modulated dual-chamber (DDDR) pacing as compared to ventricular-based (VVI) pacing. The benefits in A-V sequential pacing with the DDDR mode are likely mitigated by the interventricular (V-V) dysynchrony imposed by the high percentage of ventricular pacing commonly seen in the DDDR mode. Programming DDDR pacemakers to encourage intrinsic A-V conduction and reduce right ventricular pacing will likely decrease heart failure and pacemaker syndrome. Studies are currently ongoing to address these questions