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261.
Light detection and ranging (LIDAR) systems are able to measure the speed of incoming wind before it reaches a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine structural loads. However, the degree to which such preview‐based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. This study examines the accuracy of different measurement scenarios that rely on coherent continuous‐wave or pulsed Doppler LIDAR systems, in terms of root‐mean‐square measurement error, to determine their applicability to feedforward control. In particular, the impacts of measurement range, angular offset of the LIDAR beam from the wind direction, and measurement noise are studied for various wind conditions. A realistic simulation case involving a scanning LIDAR unit mounted in the spinner of a MW‐scale wind turbine is studied in depth, with emphasis on preview distances that provide minimum measurement error for a specific scan radius. Measurement error is analyzed for LIDAR‐based estimates of point wind speeds at the rotor as well as spanwise averaged blade effective wind speeds. The impact of turbulence structures with high coherent turbulent kinetic energy on measurement error is discussed as well. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
262.
Alireza Rezaie Rod Shahin Borhani Farzaneh Shemirani 《European Food Research and Technology》2006,223(5):649-653
Cloud point extraction has been used for preconcentration of trace amount of manganese. The analyte was complexed with 1-(2-pyridylazo)-2-naphtol (PAN) and Triton X-114 was added as surfactant. After phase separation, based on the cloud point of the mixture, and dilution of the surfactant-rich phase with methanol, the enriched analyte was determined by flame atomic absorption spectrometry. After optimization of the complexation and extraction conditions, enhancement factor of 49.1 was obtained. The detection limit was 0.39 ng ml−1 for manganese. The proposed method was applied to the determination of manganese in milk and water samples. 相似文献
263.
Transport of strontium and cesium in simulated hanford tank waste leachate through quartz sand under saturated and unsaturated flow 总被引:1,自引:0,他引:1
We investigated the effects of water saturation and secondary precipitate formation on Sr and Cs transport through quartz sand columns under saturated and unsaturated flow. Column experiments were conducted at effective water saturation ranging from 0.2 to 1.0 under steady-state flow using either 0.1 M NaNO(3) or simulated tank waste leachate (STWL; 1 M NaNO(3) and 1 M NaOH) mimicking Hanford (Washington, USA) tank waste. In 0.1 M NaNO(3) columns, Sr transported like a conservative tracer, whereas Cs was retarded relative to Sr. The transport of Sr and Cs in the 0.1 M NaNO(3) columns under all water saturations could be described with the equilibrium convection-dispersion equation (CDE). In STWL columns, Sr mobility was significantly reduced compared to the 0.1 M NaNO(3) column, because Sr was incorporated into or sorbed to neo-formed secondary precipitates. Strontium sequestration by precipitates was confirmed by additional batch and electron micrograph analyses. In contrast(,) the transport of Cs was less affected by the STWL; retardation of Cs in STWL columns was similar to that found in 0.1 M NaNO(3) columns. Analysis of STWL column data revealed that both Sr and Cs breakthrough curves showed nonideal behavior that suggest nonequilibrium conditions, although nonlinear geochemical behavior cannot be ruled out. 相似文献
264.
Stephan K Kelly M McClure R Seubsman SA Yiengprugsawan V Bain C Sleigh A;Thai Cohort Study Team 《Accident; analysis and prevention》2011,(3):1062-1067