Effect of load reduction mechanisms on loads and blade bearing movements of wind turbines

The power control of wind turbines is usually realized via a change in the pitch angle of the rotor blades. Pitching facilitates the exact control of the turbines and the reliable deceleration of the rotor when required. Pitch movements can moreover be used for load control. One of these methods is called individual pitch control (IPC). IPC controls the blades individually and brings about a significant reduction in the fatigue loads and extreme loads placed on the structural components, while at the same time reducing the yield of the turbine only slightly. The lower loads reduce material costs, and thus, the cost of energy (CoE) is reduced, despite the slight reduction in yield. The method is nevertheless not used everywhere since the additional movement cycles put the rotor blade bearings in particular under stress. Special attention must be paid to small amplitude oscillating movements, which carry a high risk of inducing surface damage in the rolling contacts of the blade bearings. This paper uses a cycle analysis of the IWT7.5‐164 reference turbine to illustrate the differences in the movement patterns of wind turbine blade bearings with and without IPC. Moreover, model calculations with single contacts are used to show which of the movement patterns carries a risk of inducing surface damage. The use of IPC leads to the expected load reduction at the blade root. In current literature, IPC is usually assumed to have a negative influence on the life expectancy of blade bearings, but the findings of this study contradict this. The summed blade bearing movement is increased, although the number of very small pitch angles occurring is reduced. This reduction reduces the risk of wear in the blade bearings.     

Novel Potential Enantioselective Phase Transfer Catalysts Based on Lupinine

Ten N-alkylated lupininium derivatives 5–8 were prepared as potential enantioselective phase transfer catalysts. Compounds 5a–d , 6a–d contain four asymmetric centers (including one in the side chain) with known configuration resting on an X-ray structure. Preliminary PT catalytic experiments in several reactions gave high chemical yields but relatively disappointing enantioselectivities.     

Intersublevel Spectroscopy on Single InAs-Quantum Dots by Terahertz Near-Field Microscopy

Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature line width of 5-8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field microspectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)(3).     

Dioxins, dioxin-like PCBs and non-dioxin-like PCBs in dairy products on the German market and the temporal tendency in Schleswig-Holstein

140 Milcherzeugnisse aus verschiedenen Regionen Deutschlands wurden 2006 auf Dioxine, dioxin?hnliche PCB und nicht dioxin?hnliche PCB untersucht. Insgesamt wurden 66 K?se-, 23 Butter- und 51 Quark- bzw. Joghurterzeugnisse analysiert. Die Probenahme erfolgte in Superm?rkten und Einzelhandelsgesch?ften auf der Basis der Produktionsmengen in den einzelnen Bundesl?ndern der Bundesrepublik Deutschland. Die Dioxinkonzentrationen und die Summe der WHO-TEQ blieben weit unter den EU-Grenzwerten von 3 pg WHO-PCDD/F-TEQ/g Fett und 6 pg WHO-PCDD/F-PCB-TEQ/g Fett. Die Dioxingehalte lagen bei niedrigen 0,07–0,53 pg WHO-PCDD/F-TEQ/g Fett mit einem arithmetischen Mittelwert von 0,19 pg WHO-PCDD/F-TEQ/kg Fett. Die WHO-PCDD/F-PCB-TEQ Gehalte lagen zwischen 0,21 und 2,1 pg WHO-TEQ/g Fett, mit einem mittleren Gehalt von 0,76 pg WHO-TEQ/g Fett. Regionale Abh?ngigkeiten und Unterschiede zwischen den einzelnen Produktgruppen konnten nicht festgestellt werden. Langj?hrige Messungen der Dioxingehalte in Butter und K?se aus Schleswig-Holstein zeigen über den Zeitraum von 13 Jahren eine deutliche Abnahme der Gehalte von 0,43 auf 0,19 pg WHO-PCDD/F-TEQ/g Fett.     

Sydnon-äthylene. I Stereoselektive Darstellung von Sydnon-äthylenen aus Sydnon-aldehyden

Sydnone Ethylenes. I Stereoselective Synthesis of Sydnone Ethylenes from Sydnone Aldehydes Sydnones are formylated in 4-position by the VILSMEIER -HAAK reaction. N(3)-Methyl- and N(3)-(p-Anisyl)-sydnone-(4)-carboxaldehyde react stereoselectively to sydnone ethylenes with diethyl ethoxycarbonylmethanephosphonate by HORNER reaction and with arylmethylphosphonium salts by WITTIG reaction in the presence of strong bases. In the latter case, especially in the absence of lithium cations, Z-selectivity is observed which is explained by electronic interaction between the sydnone cyclus and the aromatic substituent of the phosphine ylid in the first step of the reaction. The configuration of the obtained Z- and E-sydnone ethylenes is determined by means of ¹H-NMR- and IR-spectra.     

Der Versuch einer großen Integration

The long established German Society for Internal Medicine (DGIM) profoundly incriminated itself through its actions and positions during the National Socialist era. The German clinical physician Paul Martini assumed the part of reorganizing the DGIM prior to its first post-war convention in 1948 in Karlsruhe. Martini, who himself had opposed the Nazi regime, adopted a course of comprehensive integration. He strived to incorporate both physicians who had been persecuted by the Nazi Regime as well as former moderate National Socialists into the DGIM. At the same time he campaigned to preserve the pan-German nature of the conferences and aimed rapidly to make the DGIM re-compatible with international research. However, this path led to an allegedly apolitical focus on science and decades of largely failing to confront its Nazi past.     

Gestaltung der nächsten Inkarnation von Business Intelligence

The body of knowledge generated by Business Intelligence (BI) research is constantly extended by a stream of heterogeneous technological and organizational innovations. This paper shows how these can be bundled to a new vision for BI that is aligned with new requirements coming from socio-technical macro trends. The building blocks of the vision come from five research strings that have been extracted from an extensive literature review: BI and Business Process Management, BI across enterprise borders, new approaches of dealing with unstructured data, agile and user-driven BI, and new concepts for BI governance. The macro trend of the diffusion of cyber-physical systems is used to illustrate the argumentation. The realization of this vision comes with an array of open research questions and requires the coordination of research initiatives from a variety of disciplines. Due to the embedded nature of the addressed topics within general research areas of the Information Systems (IS) discipline and the linking pins that come with the underlying Dynamic Capabilities Approach such research provides a contribution to IS.     

Polyacrylamide bei der steinkohlenaufbereitung

By means of lab scale studies and electrochemical potential measurements it was shown that by selective flocculation using combinations of low molecular anionic polyelektrolytes and high molecular flocculants a coal slurry can be separated into a high ash content slurry and a thickened coal sludge. The dispersed matter contains almost only ultrafine mineral particles of high ash content. The flocculated coal particles which are virtually free of ultrafine mineral can now be treated in a highly efficient flotation step and dewatered to rather low water contents on vacuum filters.