Dynamic response analysis of wind turbines under blade pitch system fault,grid loss,and shutdown events

This study focuses on the dynamic responses of land‐based and floating wind turbines under blade pitch system fault and emergency shutdown conditions. The NREL 5 MW turbine is studied. A hydraulic pitch system is considered, and the faults under study are events with a seized blade or a blade running out of control. Emergency shutdown is defined as a fast pitch‐to‐feather maneuver of the blades. Load cases with power production and grid fault with ensuing shutdown are also analysed for comparison. The fault scenarios and the blades' fast pitching activity are simulated using HAWC2 through external Dynamic Link Libraries. On the basis of the time‐domain simulations, the response characteristics of the land‐based and the floating turbines in the four design load cases are compared. The load effects from the fault conditions are compared with the operational cases. Strong system dynamics and resonant responses, such as the tower elastic mode and the yaw resonant response, are elicited during shutdown. If the pitch system has a fault and one blade is hindered from normal pitching, the uneven load distribution of the blades leads to large structural and motion responses. For both turbines, the response maxima vary cyclically with the instantaneous azimuth when the blades start pitching to feather. For the floating wind turbine, the interaction of waves and wind also affects the results. The effect of the pitch rate during shutdown is analysed. The responses of the land‐based turbine in grid loss and shutdown conditions are proportional to the pitch rate, whereas decreased sensitivity is found in the cases with pitch system faults. For the floating turbine, the effect of the pitch rate is small, and reduced pitch and yaw motion extremes are observed as the pitch rate increases. Copyright © 2013 John Wiley & Sons, Ltd.     

A comparative study between experimentally measured mechanical attributes and users’ perception of soft feel coatings: Correlating human sense with surface characteristics of polyurethane based coatings

Different soft feel coating formulations using waterborne resins composed of soft and hard polyurethane resins were prepared. The effects of resins mixtures on the soft feel properties were studied. Attempts were made to find out the correlation between users perception and experimentally measured surface characteristics of the coatings. To this end, 72 people were asked to touch the coatings in a similar testing environment and to express their feeling in order to rank them between 1 (lowest soft feel effect) and 4 (highest soft feel effect). The coatings physical characteristics were studied by tensile test, micro Vickers hardness, atomic force microscope (AFM) and friction coefficient measurement. It was shown that the mixtures of 25:75 of soft and hard resins resulted in the best soft feel effect. Users did not consider low or high hardness films as soft. Instead, those coatings having greater toughness were ranked as the best soft feel effect. Also, coatings with lower friction coefficient and lower surface roughness were preferred by users. However, the lowest friction coefficient did not result in the best soft feel appeal. In fact, the mechanical properties, surface roughness and friction coefficient were found to play as the criteria to show soft feel effect. It is thus concluded that by selecting appropriate surface characteristics of coatings related to soft feel effect, good agreement between these properties and human feeling can be made.     

Wireless amperometric neurochemical monitoring using an integrated telemetry circuit

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order Delta Sigma modulator (Delta Sigma M) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 microm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of approximately 250 fA, approximately 1.5 pA, approximately 4.5 pA, and approximately 17 pA were achieved for input currents in the range of +/-5, +/-37, +/-150, and +/-600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 microM wirelessly over a transmission distance of approximately 0.5 m in flow injection analysis experiments.     

Modified three rail shear fixture (ASTM D 4255/D 4255M) and an experimental study of nonlinear in-plane shear behaviour of FRC

In order to understand the nature of nonlinearity in the in-plane shear behaviour of fibre reinforce composites (FRC), experimental data of such materials under loading cycles, involving loading, unloading, reversed loading and unloading from reversed loading, are essential. Using the standard ASTM D 4255/D 4255 M method, it will require the fixture to be subjected to tension as well as compression. It has been proven in this paper that the standard ASTM D 4255/D 4255 M fixture is incapable of delivering such data as premature buckling is expected when the fixture is under tension, even though it claimed that the fixture could be loaded in tension as well as in compression. A cyclic rail shear fixture (CRSF) as a modified version of ASTM D 4255/D 4255 M fixture has been proposed in this paper and it has been designed and manufactured. The new fixture, which maintains all the capabilities of its standard counterpart, is truly capable of sustaining loading in tension as well as in compression so that specimens can be tested for loading and reversed loading. A series of experiments have been carried out using the new fixture to characterise the nonlinear in-plane shear stress–strain relationship of unidirectional fibre reinforced composite specimens under various cyclic loading conditions. Some new experimental data of this nature are presented in this paper, which are novel in contents and crucial in guiding the formulation of theoretical models for the nonlinear behaviour of in-plane shear for general applications.     

Uncooled InAs-GaSb type-II infrared detectors grown on GaAssubstrates for the 8-12-μm atmospheric window

We report on the growth and characterization of type-II infrared detectors with an InAs-GaSb superlattice active layer for the 8-12-μm atmospheric window at 300 K. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. Photoconductive detectors fabricated from the superlattices showed 80% cutoff at about 12 μm at room temperature. The responsivity of the device is about 2 mA/W with a 1-V bias (E=5 V/cm) and the maximum measured detectivity of the device is 1.3×10⁸ cm.Hz^1/2/W at 11 μm at room temperature. The detector shows very weak temperature sensitivity. Also, the extracted effective carrier lifetime, τ=26 ns, is an order of magnitude longer than the carrier lifetime in HgCdTe with similar bandgap and carrier concentration     

Degradation of natural organic matter in surface water using vacuum-UV irradiation

The use of vacuum-UV (VUV) radiation to degrade natural organic matter (NOM) and the main variables affecting the efficiency of this process were investigated using an annular photoreactor. After 180 min of irradiation with VUV, the total organic carbon (TOC) decreased from 4.95 ppm to 0.3 ppm. Also, decadic absorption coefficients of the water at 185 nm and 254 nm decreased from 3.2 cm(-1) to 2.85 cm(-1), and 0.225 cm(-1) to 0 cm(-1), respectively. The reactor operation was kinetically controlled for Reynolds numbers greater than 600, changes of pH between 5 and 9 had little effect, and increases in alkalinity decreased the process efficacy. Additionally, H(2)O(2)/VUV and VUV processes were compared to H(2)O(2)/UV and UV processes, where the formers showed greater effectiveness with complete mineralization of NOM as opposed to partial oxidation with H(2)O(2)/UV, and no mineralization with UV alone. Modeling and analysis of the photon flux and absorption in the reactor showed that 99% of the 185 nm radiation was absorbed by the water in the reactor. In comparison, only 48% of the 254 nm radiation was absorbed by the water. The overall quantum efficiency of the mineralization for VUV was 0.10 for 50% TOC reduction.     

Using UV pretreatment to enhance biofiltration of mixtures of aromatic VOCs

Mixtures of airborne toluene and o-xylene, two relatively recalcitrant volatile organic compounds (VOCs), were treated effectively using integrated UV-biofiltration. The set-up consisted of a biofilter receiving UV-pretreated stream and a reference biofilter receiving no pretreatment. Experimental conditions included UV fluences of 6 and 12 mJcm(-2) as well as air flow rates of 6.3 and 9.4 Lmin(-1), corresponding to biofilter empty bed retention times (EBRTs) of 45 and 30s, respectively. The inlet concentration of organics (toluene and o-xylene) ranged between 70 and 650 mg(carbon)m(-3). The UV-biofilter consistently provided removal efficiencies of greater than 95% over the range of toluene and o-xylene inlet concentrations. Also, the coupled UV-biofiltration system provided up to 60% additional contaminant removal compared to the sum of that offered by UV and reference biofilter, demonstrating the synergistic effect of UV on biofilter performance. The UV photooxidation partially oxidized a fraction of toluene and o-xylene into water soluble and more biodegradable intermediates, such as acetaldehyde and formaldehyde, which were readily removed in the downstream biofilter. These intermediates along with up to 20ppmv ozone, formed through the photolysis of oxygen by 185 nm UV, contributed to the enhanced degradation of parent VOCs in the biofilter as well as the absence of any inhibitory effects of the VOCs on one another. Also, the presence of ozone helped control the growth of excess biofilm in the UV-coupled biofilter. While the standalone biofilter showed significant pressure drop increase (of up to 14 mm H(2)Om(-1) of the bed) over the course of experiment, the UV-coupled biofilter maintained a relatively low pressure drop of less than 3 mmH(2)Om(-1) of the bed.     

Evaluation and Comparison of Conventional and Advanced Oxidation Processes for the Removal of PPCPs and EDCs and Their Effect on THM-Formation Potentials

Pharmaceuticals and personal care products (PPCPs), endocrine disrupting compounds (EDCs) and disinfection by-products are suspected to have potential adverse impact on humans and hence their elimination during drinking water treatment is often desired or regulated. Based on pilot-plant experiments with three raw water sources, conventional treatment poorly removed the selected PPCPs and EDCs, while ozone/H₂O₂ and UV/H₂O₂ (both) with conventional treatment effectively removed PPCPs and EDCs. In most of the experiments, ozone/H₂O₂ + conventional treatment additionally removed THM formation potentials (THM-FPs) compared to those of conventional treatment. However, UV/H₂O₂ treatment was found to increase THM-FPs compared to conventionally treated water.