ALBERT

Beschreibung: A trajectory-tracking approach for a parallel kinematic manipulator with flexible links is investigated with respect to its robustness to undesired initial oscillations. For this purpose, an inverse fuzzy arithmetical scheme is presented and applied, in order to estimate allowable bounds on the initial conditions such that a certain tolerance band around the desired trajectory is not violated. The uncertainty bounds on the initial conditions obtained from this identification procedure indicate the influence of the disturbances on the tracking error, and thus also the robustness and the performance of the control scheme. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Beschreibung: Nonspherical drops are of interest in the formation of microcapsules in life sciences like food, pharmacy, and cosmetics, agro and fine chemicals as well as material sciences. Out of many systems, particle-stabilized emulsion drops, so-called Pickering emulsions, exhibit an interesting formulation. Systems with Pickering particles applied in an excess amount were investigated. During deformation, the particles fully covered the enlarged drop interfaces and prevented its relaxation to a spherical drop shape. Nonspherical drops could be produced in simple shear flow using an adequate process routine. The production in a simple device is a promising high-throughput alternative to microfluidic devices. Nonspherical drops are of increasing interest in the formation of microcapsules in life as well as material sciences. The production of nonspherical drops in simple shear flow is demonstrated. The drops are stabilized by particles which are situated in the interface and prevent the drops' relaxation. This simple approach is a promising high-throughput alternative to microfluidic devices.

Beschreibung: Abstract We report on laboratory and field Raman spectroscopy experiments on the structure of water in sea water and describe this as a function of temperature and pressure. The Raman spectrum of water/seawater is dominated by the water stretching mode band with a frequency shift in the range 2,800–3,800 cm−1. Here the hydrogen bonded (HB) clusters of several water molecules and nonhydrogen bonded (nHB, singlet H2O) forms are revealed with an isoskedastic point, similar to the isosbestic point for pH sensitive dyes. This band can be deconvolved into five Gaussian peaks, each with a specific spectroscopic assignment. We find that within the temperature range of 0–40 °C the vastly greater mass and volume of ocean water (78–85%) is in the HB forms, dominantly as (H2O)5. Without hydrogen bonding there would be no ocean, and nowhere in the bulk ocean does the simple H2O molecule exceed 20% of the total. The fraction of water molecules in the solvation shell around ions in seawater represents a third type of water, bound to an ion but not hydrogen bonded. Approximately 6% of the water molecules present at 35 salinity are in this form, and their concentration is not affected by temperature or pressure. The HB forms are a continuum of species in rapid exchange. The fraction of nHB is driven solely by temperature. We find no evidence that increased pressure changes the population of the free singlet nHB molecule; pressure drives the dominantly (H2O)5 population toward a lower volume, nested, molecular state.

Beschreibung: The performance of a model-based tracking controller depends on the quality of the underlying model. Especially for flexible multibody systems, the derivation of a suitable model and the subsequent controller design are challenging tasks. In the paper, it is shown how in a straightforward approach a feed-forward controller for a flexible multibody system is designed based on a simplified model which approximates an elastic beam by a combination of rigid beams and force elements. Furthermore, the modelling error due to this harsh simplification is included as uncertainty in the simplified model and considered in the model-based feed-forward controller design using fuzzy arithmetic. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Beschreibung: Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study is to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are: 1) exposure to climate change; 2) sensitivity to altered environmental conditions; and 3) resilience potential. Our vulnerability framework includes 1,685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18,783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrologic habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers less than 25% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies. This article is protected by copyright. All rights reserved.

Beschreibung: This paper introduces the Distribution-Independent Storm Severity Index (DI-SSI). The DI-SSI represents an approach to quantify the severity of exceptional surface wind speeds of large scale windstorms that is complementary to the SSI introduced by Leckebusch et al . While the SSI approaches the extremeness of a storm from a meteorological and potential loss (impact) perspective, the DI-SSI defines the severity in a more climatological perspective. The idea is to assign equal index values to wind speeds of the same singularity (e.g. the 99th percentile) under consideration of the shape of the tail of the local wind speed climatology. Especially in regions at the edge of the classical storm track, the DI-SSI shows more equitable severity estimates, e.g. for the extra-tropical cyclone Klaus. In order to compare the indices, their relation with the North Atlantic Oscillation is studied, which is one of the main large scale drivers for the intensity of European windstorms. In order to quantify the extremity of European winter windstorms, the Distribution-independent Storm Severity Index (DI-SSI) was developed which accounts for the shape of the tail of the local wind speed distribution. This index represents an extension to the SSI developed by Leckebusch et al . Being of parametric nature, the DI-SSI shows more coherent areas of intensity and an improved correlation with the North Atlantic Oscillation especially at the edges of the classic Atlantic storm track.

Beschreibung: Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition, and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here we review literature on carbon-cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Though processes and sensitivities differ among biomes, based on expert opinion we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to re-gain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs . ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon-climate feedbacks. This article is protected by copyright. All rights reserved.