ABSTRACT A comprehensive quality assurance (QA) procedure applied to the wind velocity records of... more ABSTRACT A comprehensive quality assurance (QA) procedure applied to the wind velocity records of the automated surface observation network of the Mexican National Weather Service has been conducted for the first time. The analysis covers a total of 139 stations with site-specific measurement periods ranging from 1 to 12 years. The QA process integrates 11 QA checks grouped into 4 categories (plausible value check, internal consistency, temporal consistency, and systematic errors). The fraction of the records flagged by the quality-control (QC) filters is substantial, with nearly 26% of all wind speed records and 5% of all wind direction records showing anomalies. Most error candidates were found to fall in the systematic error and temporal consistency categories, with 10 and 12% of the cases occurring in these categories, respectively. A significant variation of data quality over time was observed, showing both a build-up of errors over time in early stations as well as the results of a learning curve in stations installed more recently. In the case of the earliest stations, installed between 1999 and 2001, a peak in anomalies is observed about 4 years after installation with a subsequent reduction and a second peak after about 10 years. While stations installed between 2002 and 2004 show similar patterns, with error frequency peaking after about 5 years, stations installed more recently, between 2002 and 2006 show a greatly improved behaviour. The results communicated in this paper should provide useful input information for validation of mesoscale wind maps and improved data assimilation procedures.
ABSTRACT The irradiation of the junction of an STM with laser light may give access to the study ... more ABSTRACT The irradiation of the junction of an STM with laser light may give access to the study of resonant effects. Since high laser intensities are required, an active compensation setup, designed to suppress the dominating nonresonant effects is used. Mixed films of the dye perylene-tetracarboxylic-dianhydride (PTCDA) and the liquid crystal octylcyanobiphenyl (8CB) were prepared on graphite and MoS2. STM measurements show small isolated domains of PTCDA embedded in 8CB. The islands could be imaged with high resolution even under the illumination with intense laser light. First experiments investigating the laser-induced contrast observed on the dye islands under active compensation of the nonresonant effects are discussed.
... It was shown that for a highly corrugated gold film on mica the contrast of the c3I/OP image ... more ... It was shown that for a highly corrugated gold film on mica the contrast of the c3I/OP image - except for very low scanning velocities - is dominated by the ... 66, 1717 (1991) 5. AA Lucas, PH Cutler, TE Feuchtwang, TT Tsong, TE Sullivan, Y. Kuk, H. Nguyen, PJ Silverman: J. Vac. ...
This paper presents the integration of an artificial neural network (ANN) based control algorithm... more This paper presents the integration of an artificial neural network (ANN) based control algorithm for minimizing the stress of a wind turbine (WT) operating above-rated wind speeds, and a coupled aeroelastic model derived from structural blade element momentum (BEM) and thin-walled beam (TWB) theory. The coupled BEM/TWB model is used for real-time determination of stress, strain and displacement in arbitrary positions of rotating blades. The controller selected is a proportionalintegral-derivate (PID) whose tuning parameters are calculated online through an Adaline ANN. The results show significant improvements in the stress reduction on the blades through the verification of a normalized stress factor. The stress reduction with the proposed control algorithm is up to 27%.
Journal of vacuum science & technology, Mar 1, 1991
An atomic force microscope is presented which uses the tunneling effect for signal detection, the... more An atomic force microscope is presented which uses the tunneling effect for signal detection, the tunneling tip-to-sensor approach being based on an inertial sliding mechanism. Concentric tube piezo arrangements of both the sample and slider mounts serve for thermal drift compensation. Particular emphasis lies on the description of the sliding device, sawtooth voltage generation and control for the slider motion, and tip feedback electronics. The image of a 4.7×4.7 μm2 surface section of an optical storage disk illustrates the large-scale scanning performance of the instrument.
Structural Health Monitoring-an International Journal, 2011
Development of an integrated Fiber Bragg Grating (FBG) structural health monitoring (SHM) system ... more Development of an integrated Fiber Bragg Grating (FBG) structural health monitoring (SHM) system for a composite horizontal axis wind turbine blade is reported in this article. The SHM systems are expected to make significant reduction in the operational cost of wind turbines by optimizing the maintenance, yielding maximum service life of the wind turbine at minimum maintenance cost. Recently, the SHM systems are receiving even more attention due to the current trend in designing larger wind turbines in order to increase the efficiency. Increasing their size subjects them to larger operational loads and thus demands precise and real-time information about how the system is performing. The FBG sensor as SHM sensor has many advantages over other conventional sensors. Providing real-time information about structural integrity and operational load can be used in conjunction with other methods to decrease the overall energy cost. This paper discusses laboratory scale experimental setup f...
ABSTRACT The knowledge of the apparent motion of the Sun - due to the combined effects of the rot... more ABSTRACT The knowledge of the apparent motion of the Sun - due to the combined effects of the rotation of the Earth around its proper axis and the translation around the Sun - is important both in natural and man-made systems. In particular, a proper explanation of the seasons requires an understanding of this solar geometry. In this paper we present a simple derivation of the relevant formulae based on vector algebra. The possible trajectories are discussed in detail. An approximate explicit formula for the seasonal variations of solar radiation is derived and discussed. The calculations give useful insights into the geometry of the problem and are thought to be helpful for the undergraduate teaching of solar energy engineering, classical mechanics and astronomy.
ABSTRACT A comprehensive quality assurance (QA) procedure applied to the wind velocity records of... more ABSTRACT A comprehensive quality assurance (QA) procedure applied to the wind velocity records of the automated surface observation network of the Mexican National Weather Service has been conducted for the first time. The analysis covers a total of 139 stations with site-specific measurement periods ranging from 1 to 12 years. The QA process integrates 11 QA checks grouped into 4 categories (plausible value check, internal consistency, temporal consistency, and systematic errors). The fraction of the records flagged by the quality-control (QC) filters is substantial, with nearly 26% of all wind speed records and 5% of all wind direction records showing anomalies. Most error candidates were found to fall in the systematic error and temporal consistency categories, with 10 and 12% of the cases occurring in these categories, respectively. A significant variation of data quality over time was observed, showing both a build-up of errors over time in early stations as well as the results of a learning curve in stations installed more recently. In the case of the earliest stations, installed between 1999 and 2001, a peak in anomalies is observed about 4 years after installation with a subsequent reduction and a second peak after about 10 years. While stations installed between 2002 and 2004 show similar patterns, with error frequency peaking after about 5 years, stations installed more recently, between 2002 and 2006 show a greatly improved behaviour. The results communicated in this paper should provide useful input information for validation of mesoscale wind maps and improved data assimilation procedures.
ABSTRACT The irradiation of the junction of an STM with laser light may give access to the study ... more ABSTRACT The irradiation of the junction of an STM with laser light may give access to the study of resonant effects. Since high laser intensities are required, an active compensation setup, designed to suppress the dominating nonresonant effects is used. Mixed films of the dye perylene-tetracarboxylic-dianhydride (PTCDA) and the liquid crystal octylcyanobiphenyl (8CB) were prepared on graphite and MoS2. STM measurements show small isolated domains of PTCDA embedded in 8CB. The islands could be imaged with high resolution even under the illumination with intense laser light. First experiments investigating the laser-induced contrast observed on the dye islands under active compensation of the nonresonant effects are discussed.
... It was shown that for a highly corrugated gold film on mica the contrast of the c3I/OP image ... more ... It was shown that for a highly corrugated gold film on mica the contrast of the c3I/OP image - except for very low scanning velocities - is dominated by the ... 66, 1717 (1991) 5. AA Lucas, PH Cutler, TE Feuchtwang, TT Tsong, TE Sullivan, Y. Kuk, H. Nguyen, PJ Silverman: J. Vac. ...
This paper presents the integration of an artificial neural network (ANN) based control algorithm... more This paper presents the integration of an artificial neural network (ANN) based control algorithm for minimizing the stress of a wind turbine (WT) operating above-rated wind speeds, and a coupled aeroelastic model derived from structural blade element momentum (BEM) and thin-walled beam (TWB) theory. The coupled BEM/TWB model is used for real-time determination of stress, strain and displacement in arbitrary positions of rotating blades. The controller selected is a proportionalintegral-derivate (PID) whose tuning parameters are calculated online through an Adaline ANN. The results show significant improvements in the stress reduction on the blades through the verification of a normalized stress factor. The stress reduction with the proposed control algorithm is up to 27%.
Journal of vacuum science & technology, Mar 1, 1991
An atomic force microscope is presented which uses the tunneling effect for signal detection, the... more An atomic force microscope is presented which uses the tunneling effect for signal detection, the tunneling tip-to-sensor approach being based on an inertial sliding mechanism. Concentric tube piezo arrangements of both the sample and slider mounts serve for thermal drift compensation. Particular emphasis lies on the description of the sliding device, sawtooth voltage generation and control for the slider motion, and tip feedback electronics. The image of a 4.7×4.7 μm2 surface section of an optical storage disk illustrates the large-scale scanning performance of the instrument.
Structural Health Monitoring-an International Journal, 2011
Development of an integrated Fiber Bragg Grating (FBG) structural health monitoring (SHM) system ... more Development of an integrated Fiber Bragg Grating (FBG) structural health monitoring (SHM) system for a composite horizontal axis wind turbine blade is reported in this article. The SHM systems are expected to make significant reduction in the operational cost of wind turbines by optimizing the maintenance, yielding maximum service life of the wind turbine at minimum maintenance cost. Recently, the SHM systems are receiving even more attention due to the current trend in designing larger wind turbines in order to increase the efficiency. Increasing their size subjects them to larger operational loads and thus demands precise and real-time information about how the system is performing. The FBG sensor as SHM sensor has many advantages over other conventional sensors. Providing real-time information about structural integrity and operational load can be used in conjunction with other methods to decrease the overall energy cost. This paper discusses laboratory scale experimental setup f...
ABSTRACT The knowledge of the apparent motion of the Sun - due to the combined effects of the rot... more ABSTRACT The knowledge of the apparent motion of the Sun - due to the combined effects of the rotation of the Earth around its proper axis and the translation around the Sun - is important both in natural and man-made systems. In particular, a proper explanation of the seasons requires an understanding of this solar geometry. In this paper we present a simple derivation of the relevant formulae based on vector algebra. The possible trajectories are discussed in detail. An approximate explicit formula for the seasonal variations of solar radiation is derived and discussed. The calculations give useful insights into the geometry of the problem and are thought to be helpful for the undergraduate teaching of solar energy engineering, classical mechanics and astronomy.
Uploads
Papers